Misplaced Pages

Hearing aid: Difference between revisions

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Browse history interactively← Previous editContent deleted Content addedVisualWikitext
Revision as of 20:32, 17 July 2006 edit66.142.210.68 (talk)No edit summary← Previous edit Latest revision as of 12:44, 13 December 2024 edit undoSjö (talk | contribs)Extended confirmed users, New page reviewers, Pending changes reviewers, Rollbackers58,616 editsm Reverted edits by 165.0.3.9 (talk) to last version by MidnightAlarmTag: Rollback 
Line 1: Line 1:
{{short description|Electroacoustic device}}
]
{{Use dmy dates|date=May 2024}}
Al Gore invented the hearing aid.
{{Infobox medical intervention
| name = Hearing aid
| synonym = Deaf aid
| image = Hearing aid 20080620.jpg
| caption = In-the-canal hearing aid
| alt =
| pronounce =
| specialty = <!-- from Wikidata, can be overwritten -->
| synonyms =
| ICD10 =
| ICD9 =
| ICD9unlinked =
| CPT =
| MeshID =
| LOINC =
| other_codes =
| MedlinePlus =
| eMedicine =
}}


A '''hearing aid''' is a device designed to improve hearing by making sound audible to a person with ]. Hearing aids are classified as ]s in most countries, and regulated by the respective regulations. Small audio amplifiers such as ] (PSAPs) or other plain sound reinforcing systems cannot be sold as "hearing aids".
A '''hearing aid''' is a device used to help ] people ] sounds better. In the past, a ]-like amplification cone, called an "ear trumpet" or "ear horn", was used. Also sometimes used was a desk with a built-in
amplifier into which a microphone and earphones could be plugged; these worked better
than passive ear trumpets but were not portable.


Early devices, such as ]s or ear horns,<ref>{{cite journal | vauthors = Bentler RA, Duve MR | date = December 2000 |title=Comparison of hearing aids over the 20th century |journal=Ear and Hearing |volume=21 |issue=6 |pages=625–639 |doi=10.1097/00003446-200012000-00009 |pmid=11132788 |s2cid=46218426 }}</ref><ref>{{Cite web |title=Ear Horn Q&A |url=http://www.hearingcenter.com/Questions/Q_ear-horn.html |archive-url=https://web.archive.org/web/20080724231030/http://www.hearingcenter.com/Questions/Q_ear-horn.html |archive-date=24 July 2008 |access-date=6 December 2007}}</ref> were passive ] cones designed to gather sound energy and direct it into the ear canal.
Now, however, the most common style is a small ] device that fits into the wearer's ]. The first variety of this device had a ] ] pack connected by a thin wire, intended to be held in a ]. Such "body aids," though much more portable than the desk type, still
suffered significant disadvantages due to sub-optimal microphone placement. Since the microphone was not near the user's
head, it was susceptible to interfering sounds such as clothing-noise. Sound input was also distorted if the microphone was located below the mouth of a person with whom the user was conversing.


{{Wikiversity|Global Audiology}}
During the mid- to late ], hearing aids that were carried in pockets were replaced by a more inconspicuous sort of model in which small ] were placed in the inserted unit itself.


Modern devices are computerised electroacoustic systems that transform environmental sound to make it audible, according to ] and ] rules. Modern devices also utilize sophisticated digital signal processing, aiming to improve speech intelligibility and comfort for the user. Such ] includes feedback management, wide dynamic range compression, directionality, frequency lowering, and noise reduction.
==Types of hearing aids==

There are many types of hearing aids, which vary in size, power and ].
Modern hearing aids require configuration to match the hearing loss, physical features, and lifestyle of the wearer. The hearing aid is fitted to the most recent ] and is programmed by frequency. This process called "fitting" can be performed by the user in simple cases, by a Doctor of ], also called an audiologist (AuD), or by a Hearing Instrument Specialist (HIS) or ]. The amount of benefit a hearing aid delivers depends in large part on the quality of its fitting. Almost all hearing aids in use in the US are digital hearing aids, as analog aids are phased out.<ref name="lww">{{Cite journal |last=Kochkin |first=Sergei |date=January 2010 |title=MarkeTrak VIII: Consumer satisfaction with hearing aids is slowly increasing |journal=The Hearing Journal |volume=63 |issue=1 |pages=19–20 |doi=10.1097/01.HJ.0000366912.40173.76 |s2cid=73880581 | doi-access = free | title-link = doi | name-list-style = vanc }}</ref> Devices similar to hearing aids include the osseointegrated auditory prosthesis (formerly called the ]) and ].
{{TOC limit|3}}

==Uses==
Hearing aids are used for a variety of pathologies including ], ], and ]. Hearing aid candidacy was traditionally determined by a Doctor of Audiology, or a certified hearing specialist, who will also fit the device based on the nature and degree of the hearing loss being treated. The amount of benefit experienced by the user of the hearing aid is multi-factorial, depending on the type, severity, and etiology of the hearing loss, the technology and fitting of the device, and on the motivation, personality, lifestyle, and overall health of the user.<ref>{{Cite journal | vauthors = Cox RM, Johnson JA, Xu J |date=July 2016 |title=Impact of Hearing Aid Technology on Outcomes in Daily Life I: the Patients' Perspective |journal=Ear and Hearing |volume=37 |issue=4 |pages=e224–37 |doi=10.1097/AUD.0000000000000277 |pmc=4925253 |pmid=26881981 }}</ref> Over-the-counter hearing aids, which address mild to moderate hearing loss, are designed to be adjusted by the user.<ref>{{cite news |title=The Best Over-the-Counter Hearing Aids and Other Hearing Solutions |work=The New York Times |url=https://www.nytimes.com/wirecutter/reviews/best-over-the-counter-hearing-aids/ |access-date=5 December 2022 |archive-date=14 January 2023 |archive-url=https://web.archive.org/web/20230114150020/https://www.nytimes.com/wirecutter/reviews/best-over-the-counter-hearing-aids/ |url-status=live }}</ref>

Hearing aids are incapable of truly correcting a hearing loss; they are an ''aid'' to make sounds more audible. The most common form of hearing loss for which hearing aids are sought is sensorineural, resulting from ] and synapses of the cochlea and auditory nerve. Sensorineural hearing loss reduces the sensitivity to sound, which a hearing aid can partially accommodate by making sound louder. Other decrements in auditory perception caused by sensorineural hearing loss, such as abnormal spectral and temporal processing, and which may negatively affect speech perception, are more difficult to compensate for using digital signal processing and in some cases may be exacerbated by the use of amplification.<ref>{{Cite book |author=J. Moore |author2=Brian C. |title=Cochlear hearing loss: physiological, psychological and technical issues |date=2007 |publisher=John Wiley & Sons |isbn=978-0-470-51633-1 |edition=2nd |location=Chichester |oclc=180765972}}</ref>{{page needed|date=November 2017}} Conductive hearing losses, which do not involve damage to the cochlea, tend to be better treated by hearing aids; the hearing aid is able to sufficiently amplify sound to account for the attenuation caused by the conductive component. Once the sound is able to reach the cochlea at normal or near-normal levels, the cochlea and auditory nerve are able to transmit signals to the brain normally.

Common issues with hearing aid fitting and use are the ], loudness recruitment, and understanding speech in noise. Once a common problem, ] is generally now well-controlled through the use of feedback management algorithms.

== Candidacy and acquisition ==
There are several ways of evaluating how well a hearing aid compensates for hearing loss. One approach is ] which measures a subject's hearing levels in laboratory conditions. The threshold of audibility for various sounds and intensities is measured in a variety of conditions. Although audiometric tests may attempt to mimic real-world conditions, the patient's own every day experiences may differ. An alternative approach is self-report assessment, where the patient reports their experience with the hearing aid.<ref>{{Cite journal | vauthors = Bentler RA, Kramer SE | date = August 2000 |title=Guidelines for choosing a self-report outcome measure |journal=Ear and Hearing |volume=21 |issue=4 Suppl |pages=37S–49S |doi=10.1097/00003446-200008001-00006 |pmid=10981593 |s2cid=36628081 |doi-access=free }}</ref><ref>{{Cite web |last=Taylor |first=Brian |date=22 October 2007 |title=Self-Report Assessment of Hearing Aid Outcome – An Overview |url=http://www.audiologyonline.com/articles/self-report-assessment-hearing-aid-931 |url-status=live |archive-url=https://web.archive.org/web/20150129050620/http://www.audiologyonline.com/articles/self-report-assessment-hearing-aid-931 |archive-date=29 January 2015 |access-date=29 May 2013 |publisher=AudiologyOnline}}</ref>

Hearing aid outcome can be represented by three dimensions:<ref>{{Cite journal | last1=Humes | first1=Larry | last2=Humes | first2=Lauren | date=April 2004 |title=Factors Affecting Long-Term Hearing Aid Success |journal=Seminars in Hearing |volume=25 |issue=1 |pages=63–72 |doi=10.1055/s-2004-823048 | s2cid=260312035 | name-list-style = vanc }}</ref>
# hearing aid usage
# aided speech recognition
# benefit/satisfaction

The most reliable method for assessing the correct adjustment of a hearing aid is through ].<ref>{{Cite book |last1=Katz | first1=Jack |title=Handbook of Clinical Audiology |last2=Medwetsky, Larry |last3=Burkard, Robert |last4=Hood, Linda |publisher=Lippincott Williams & Wilkins |year=2009 |isbn=978-0-7817-8106-0 |edition=6th |location=Baltimore MD |page=858 |chapter=Chapter 38, Hearing Aid Fitting for Adults: Selection, Fitting, Verification, and Validation}}</ref> Real ear measurements (or probe microphone measurements) are an assessment of the characteristics of hearing aid amplification near the ear drum using a silicone probe tube microphone.<ref>{{Cite book |last=Stach |first=Brad |title=Comprehensive Dictionary of Audiology |publisher=Thompson Delmar Learning |year=2003 |isbn=978-1-4018-4826-2 |edition=2nd |location=Clifton Park NY |page=167}}</ref>

Current research is also pointing towards hearing aids and proper amplification as a treatment for ], a medical condition which manifests itself as a ringing or buzzing in the ears.<ref>{{Cite web |date=30 December 2016 |title=Tinnitus And Hearing Aids - Optimal Hearing Systems, The Hearing Aid Company - Since 1961 |url=https://optimalhearing.com/tinnitus-hearing-aids/ |access-date=5 July 2020 |website=Optimal Hearing |language=en-US |archive-date=6 July 2020 |archive-url=https://web.archive.org/web/20200706133906/https://optimalhearing.com/tinnitus-hearing-aids/ |url-status=live }}</ref>

==Types==
There are many types of hearing aids (also known as hearing instruments), which vary in size, ] and ].
Among the different sizes and models are: Among the different sizes and models are:
<gallery mode="packed" class="center">
File:Vintage Zenith Radionic 3-Vacuum Tube (Body) Hearing Aid, Model-A3A, Pastel Coralite Case, Bone-Air, Original Cost = 50.00 USD, Circa 1944 (10840966755).jpg|Vacuum tube hearing aid, circa 1944
File:Vintage Telex Transistor (Body) Hearing Aid, Model 70A, Made in the USA (12483173304).jpg|Transistor body-worn hearing aid.
File:BTEhearingaids.png|Pair of BTE hearing aids with earmolds.
File:Hinter-Ohr-Hörgeräte.JPG|Receiver-in-the-canal hearing aids
File:HearingAid ITE.png|In-the-ear hearing aid
File:Hearing aid cic.jpg|In-the-canal hearing aid
File:Baha user sound processor behind ear.PNG|Woman wearing a bone anchored hearing aid
File:Hearing aid application.jpg|Hearing aid application
</gallery>


===Body worn aids=== ===Body-worn===
Body worn aids were the first portable electronic hearing aids, and were invented by ] while working at ].<ref>{{Cite book |author=Hartmann, William M. |url=https://books.google.com/books?id=3N72rIoTHiEC&pg=PA72 |title=Signals, Sound, and Sensation |date=14 September 2004 |publisher=Springer Science & Business Media |isbn=978-1-56396-283-7 |pages=72– |archive-url=https://web.archive.org/web/20161203013440/https://books.google.com/books?id=3N72rIoTHiEC&pg=PA72 |archive-date=3 December 2016 |url-status=live}}</ref> Body aids consist of a case and an ], attached by a wire. The case contains the electronic ] components, controls and ], while the earmold typically contains a miniature ]. The case is typically about the size of a pack of ] and is carried in a pocket or on a belt.<ref name="NIH">{{citation
This was the first type of hearing aid, and thanks to developments in technology they are now rarely used. These aids consist of a case containing the components of ] and an ear mold connected to the case by a cord. The case is about the size of a pack of cards and is worn in the pocket or on a belt. Because of their large size, body worn aids are capable of large amounts of amplification and were once used for profound hearing losses. Today, they have largely been replaced by BTEs
|title= Hearing Aid Basics
|url= http://www.nidcd.nih.gov/health/hearing/pages/hearingaid.aspx
|publisher= National Institute of Health
|access-date= 2 December 2011
|url-status= live
|archive-url= https://web.archive.org/web/20111113160106/http://www.nidcd.nih.gov/health/hearing/pages/hearingaid.aspx
|archive-date= 13 November 2011
}}</ref>
Without the size constraints of smaller hearing devices, body worn aid designs can provide large amplification and long battery life at a lower cost. Body aids are still used in ] because of their relatively low cost.<ref name="NIH" />


===Behind the ear aids (BTE)=== ===Behind the ear===
]
BTE aids have a small case that fits behind the ear and conducts sound to the ear through an earmold that is custom made. BTEs can be used for mild to profound hearing losses and are especially useful for children because of their durability and they can easily connect to assistive listening devices such as ] systems for classroom use. BTEs can range from very inconspicuous skin tones to cheerful colors depending on the users preference. Recent innovations in BTEs include miniature "invisible" BTEs with thin hair like sound tubes (see open-fit devices below). These are often less visible than ITEs and some keep the ear canal more open, so listeners may still utilise their residual natural hearing (most helpful for those with normal hearing in the lower frequencies). Ideal for high frequency losses, these miniature versions are generally used for mild to moderate hearing loss.
]
Behind the ear hearing aids are one of two major classes of hearing aids – behind the ear (BTE) and in the ear (ITE). These two classes are distinguished by where the hearing aid is worn. BTE hearing aids consist of a case which hangs behind the ]. The case is attached to an earmold or dome tip by a traditional tube, slim tube, or wire. The tube or wire courses from the superior-ventral portion of the pinna to the concha, where the ear mold or dome tip inserts into the ]. The case contains the electronics, controls, battery, and microphone(s).The loudspeaker, or receiver, may be housed in the case (traditional BTE) or in the earmold or dome tip (receiver-in-the-canal, or RIC). The RIC style of BTE hearing aid is often smaller than a traditional BTE and more commonly used in more active populations.<ref>{{cite web |url=http://www.nidcd.nih.gov/health/hearing/pages/hearingaid.aspx |title=Hearing Aids |publisher=National Institute on Deafness and Other Communication Disorders |access-date=9 September 2012 |url-status=live |archive-url=https://web.archive.org/web/20120915171007/http://www.nidcd.nih.gov/health/hearing/pages/hearingaid.aspx |archive-date=15 September 2012 }}</ref>


BTEs are generally capable of providing more output and may therefore be indicated for more severe degrees of hearing loss. However, BTEs are very versatile and can be used for nearly any kind of hearing loss. BTEs come in a variety of sizes, ranging from a small, "mini BTE", to larger, ultra-power devices. Size typically depends on the output level needed, the location of the receiver, and the presence or absence of a telecoil. BTEs are durable, easy to repair, and often have controls and battery doors that are easier to manipulate. BTEs are also easily connected to assistive listening devices, such as ] systems and ]s. BTEs are commonly worn by children who need a durable type of hearing aid.<ref name="NIH" />
===In the ear aids (ITE)===
These devices fit in the outer ear bowl (called the ]); they are sometimes visible when standing face to face with someone. ITE hearing aids are custom made to fit each individual's ear. They can be used in mild to some severe hearing losses. ], a squealing/whistling caused by sound leaking out of the aid and being amplified again, may be a problem for severe hearing losses. Some modern circuits are able to provide feedback regulation or cancellation to assist with this. ITEs are not recommended for young children because their fit cannot be as easily modified as the earmold for a BTE, and the aid must then be replaced frequently as the child grows. By the time a person is 13-16 years old, s/he will probably be able to wear an ITE if it is appropriate for the hearing loss found.


===In the ear===
===In the canal (ITC), mostly in canal (MIC) and completely in the canal aids (CIC)===
In the ear aids (ITE) devices fit in the outer ear bowl (called the ]). Being larger, these are easier to insert and can hold extra features.<ref name="Consumer Reports">{{cite web|url=http://www.consumerreports.org/cro/hearing-aids/buying-guide.htm|title=Hearing Aid Buying Guide|date=February 2017|website=Consumer Reports|archive-url=https://web.archive.org/web/20170212023435/http://www.consumerreports.org/cro/hearing-aids/buying-guide.htm|archive-date=12 February 2017|url-status=live|access-date=13 February 2017}}</ref> They are sometimes visible when standing face to face with someone. ITE hearing aids are custom made to fit each individual's ear. They can be used in mild to some severe hearing losses. ], a squealing/whistling caused by sound (particularly high frequency sound) leaking and being amplified again, may be a problem for severe hearing losses.<ref>{{cite web |url=http://www.actiononhearingloss.org.uk/is-hearing-loss-affecting-your-family/getting-hearing-aids/problems-with-hearing-aids-ask-our-audiologist.aspx |title=Problems with hearing aids: Ask our audiologist – Action On Hearing Loss: RNID |publisher=Action On Hearing Loss |access-date=28 December 2016 |url-status=live |archive-url=https://web.archive.org/web/20160617125717/https://www.actiononhearingloss.org.uk/is-hearing-loss-affecting-your-family/getting-hearing-aids/problems-with-hearing-aids-ask-our-audiologist.aspx |archive-date=17 June 2016 }}</ref> Some modern circuits are able to provide feedback regulation or cancellation to assist with this.
ITC aids are smaller, filling only the bottom half of the external ear. You usually cannot see very much of this hearing aid when you are face to face with someone. MIC and CIC aids are even smaller and often not visible unless you look directly into the wearer's ear. They can be used for mild and sometimes moderate losses. CICs are not recommended if you have very good low frequency hearing as the complete plugged up effect may make your voice resonate in your head even if you have them switched off (the "occlusion effect").
Venting may also cause feedback. A ] is a tube primarily placed to offer pressure equalization. However, different vent styles and sizes can be used to influence and prevent feedback.<ref>Sickel, K. (13 September 2007) {{Webarchive|url=https://web.archive.org/web/20170705095832/http://www5.informatik.uni-erlangen.de/Forschung/Publikationen/2007/Sickel07-SPS.pdf |date=5 July 2017 }} ''52. IWK, Internationales Wissenschaftliches Kolloquium'' (Computer science meets automation Ilmenau 10.) Vol. 2 Ilmenau : TU Ilmenau Universitätsbibliothek 2007, pp. 221–226</ref>
Traditionally, ITEs have not been recommended for young children because their fit could not be as easily modified as the earmold for a BTE, and thus the aid had to be replaced frequently as the child grew.<ref>{{cite web|title=Hearing Aids for Children|url=http://www.asha.org/public/hearing/Hearing-Aids-for-Children/|website=Hearing Aids for Children|publisher=American Speech-Language-Hearing Association|access-date=1 December 2014|archive-date=17 August 2022|archive-url=https://web.archive.org/web/20220817044131/https://www.asha.org/public/hearing/Hearing-Aids-for-Children/|url-status=live}}</ref> However, there are new ITEs made from a ] type material that mitigates the need for costly replacements.
ITE hearing aids can be connected wirelessly to FM systems, for instance with a body-worn FM receiver with induction neck-loop which transmits the audio signal from the FM transmitter inductively to the telecoil inside the hearing instrument.


Mini in canal (MIC) or completely in canal (CIC) aids are generally not visible unless the viewer looks directly into the wearer's ear.<ref>Eisenberg, Anne (24 September 2005) {{webarchive|url=https://web.archive.org/web/20160106205158/http://www.nytimes.com/2006/09/24/business/yourmoney/24novel.html |date=6 January 2016 }}. ''NY Times''.</ref><ref>Dybala, Paul (6 March 2006) {{webarchive|url=https://web.archive.org/web/20120816035512/http://www.audiologyonline.com/articles/article_detail.asp?article_id=1542 |date=16 August 2012 }}. AudiologyOnline.com.</ref> These aids are intended for mild to moderately severe losses. CICs are usually not recommended for people with good low-frequency hearing, as the occlusion effect is much more noticeable.<ref>Ross, Mark (January 2004) {{webarchive|url=https://web.archive.org/web/20160215065655/http://www.hearingresearch.org/ross/hearing_loss/the_occlusion_effect.php |date=15 February 2016 }}, hearingresearch.org.</ref> Completely-in-the-canal hearing aids fit tightly deep in the ear.<ref name="Consumer Reports"/> It is barely visible.<ref name="Consumer Reports"/> Being small, it will not have a directional microphone, and its small batteries will have a short life, and the batteries and controls may be difficult to manage.<ref name="Consumer Reports"/> Its position in the ear prevents wind noise and makes it easier to use phones without feedback.<ref name="Consumer Reports"/> In-the-canal hearing aids are placed deep in the ear canal.<ref name="Consumer Reports"/> They are barely visible.<ref name="Consumer Reports"/> Larger versions of these can have directional microphones.<ref name="Consumer Reports"/> Being in the canal, they are less likely to cause a plugged feeling.<ref name="Consumer Reports"/> These models are easier to manipulate than the smaller completely in-the-canal models but still have the drawbacks of being rather small.<ref name="Consumer Reports"/>
For diagrams and pictures of these different types, see .


In-the-ear hearing aids are typically more expensive than behind-the-ear counterparts of equal functionality, because they are custom fitted to the patient's ear.
===Open-fit devices===
In fitting, the ] takes a physical impression (]) of the ear.
Recently a new device has come on the market, the "Open-fit" or "Over-the-Ear" OTE Hearing Aid. Usually quite discreet, these are small Behind-the-ear type devices, with a much finer clear tube that runs down into the ear canal. Inside the ear canal, there is a small soft silicone dome or a molded, highly vented acrylic tip that holds the tube in place. There are also devices available which have an external speaker, placed inside the ear canal, and connected to the hearing system itself by a thin cable. The external speaker allows the device behind the ear to be even smaller.
The mold is scanned by a specialized ] system, resulting in a 3D model of the outer ear.
These devices are designed to reduce the "occlusion effect", which is the amplification of your own voice when your ears are plugged up (try sticking your fingers in your ears and talking). Open-fit devices are very beneficial for High-Frequency hearing losses, and have been introduced by all major hearing aid companies.
During modeling, the venting tube is inserted.
The digitally modeled ''shell'' is printed using a ] technique such as ].
Finally, the aid is assembled and shipped to the audiologist after a quality check.<ref>Sickel, K. et al. (2009) {{Webarchive|url=https://web.archive.org/web/20160304063250/http://www5.informatik.uni-erlangen.de/Forschung/Publikationen/2009/Sickel09-SMO.pdf |date=4 March 2016 }}. ''Proceedings of the Vision, Modeling, and Visualization Workshop 2009'' (Braunschweig, Germany 16–18 November 2009), pp. 305–312</ref>


===Invisible-in-canal hearing aids===
===Bone Anchored Hearing Aids (BAHA)===
Invisible-in-canal hearing aids (IIC) style of hearing aids fits inside the ear canal completely, leaving little to no trace of an installed hearing aid visible. This is because it fits deeper in the canal than other types, so that it is out of view even when looking directly into the ear bowl (concha). A comfortable fit is achieved because the shell of the aid is custom-made to the individual ear canal after taking a mold.
The BAHA is a surgically implanted system that uses bone transmission as a pathway for sound to travel to the inner ear, bypassing the external auditory canal and middle ear. A titanium "post" is surgically embedded into the skull with a small abutment exposed outside the skin. A sound processor sits on this abutment and transmits sound vibrations to the external abutment of the titanium implant. The implant vibrates the skull and inner ear, which stimulate the nerve fibers of the inner ear, allowing hearing.
Invisible hearing aid types use venting and their deep placement in the ear canal to give a more natural experience of hearing. Unlike other hearing aid types, with the IIC aid the majority of the ear is not blocked (occluded) by a large plastic shell. This means that sound can be collected more naturally by the shape of the ear, and can travel down into the ear canal as it would with unassisted hearing. Depending on their size, some models allow the wearer to use a mobile phone as a remote control to alter memory and volume settings, instead of taking the IIC out to do this. IIC types are most suitable for users up to middle age, but are not suitable for elderly people with unsteady hands.<ref>{{Cite web|date=5 July 2018|title=Invisible Hearing Aids or IIC hearing aids are convenient. Will they suit you?|url=https://earguru.in/blogs/hearing-aids/pros-and-cons-of-invisible-hearing-aids/|access-date=7 June 2021|website=EarGuru Ear Health Blog|language=en-US|archive-date=17 August 2022|archive-url=https://web.archive.org/web/20220817044134/https://earguru.in/hearing-aids/invisible-hearing-aids/|url-status=live}}</ref>

===Extended wear hearing aids===
{{Main|Extended wear hearing aid}}
Extended wear hearing aids are hearing devices that are non-surgically placed in the ear canal by a hearing professional. The extended wear hearing aid represents the first "invisible" hearing device. These devices are worn for 1–3 months at a time without removal. They are made of soft material designed to contour to each user and can be used by people with mild to moderately severe hearing loss. Their close proximity to the ear drum results in improved sound directionality and localization, reduced feedback, and improved high frequency gain.<ref>{{cite journal| vauthors = Sanford MJ, Anderson T, Sanford C |title=The extended-wear hearing device: Observations on patient experiences and its integration into a practice | journal=Hearing Review|date=March 2014|volume=21|issue=3|pages=26–31|url=http://www.hearingreview.com/2014/03/extended-wear-hearing-device-observations-patient-experiences-integration-practice/|access-date=1 December 2014|url-status=live|archive-url=https://web.archive.org/web/20141205042637/http://www.hearingreview.com/2014/03/extended-wear-hearing-device-observations-patient-experiences-integration-practice/|archive-date=5 December 2014}}</ref> While traditional BTE or ITC hearing aids require daily insertion and removal, extended wear hearing aids are worn continuously and then replaced with a new device. Users can change volume and settings without the aid of a hearing professional. The devices are very useful for active individuals because their design protects against moisture and earwax and can be worn while exercising, showering, etc. Because the device's placement within the ear canal makes them invisible to observers, extended wear hearing aids are popular with those who are self-conscious about the aesthetics of BTE or ITC hearing aid models. As with other hearing devices, compatibility is based on an individual's hearing loss, ear size and shape, medical conditions, and lifestyle. The disadvantages include regular removal and reinsertion of the device when the battery dies, inability to go underwater, earplugs when showering, and for some discomfort with the fit since it is inserted deeply in the ear canal, the only part of the body where skin rests directly on top of bone.

===CROS hearing aid===
{{Main|CROS hearing aid}}
A ] is a hearing aid that transmits auditory information from one side of the head to the other side of the head. Candidates include people who have poor word understanding on one side, no hearing on one side, or who are not benefiting from a hearing aid on one side. CROS hearing aids can appear very similar to behind the ear hearing aids. The CROS system can assist the patient in sound localization and understanding auditory information on their poor side. While CROS hearing aids can be quite effective, the long-term solution for those with hearing issues on one side is to use a BiCROS system.{{citation needed|date=January 2022}} This creates more of a balance for wearers.

===Bone-anchored===
{{Main|Bone anchored hearing aid}}
A ] (BAHA) is a ] ] ] ] based on bone conduction. It is an option for patients without external ear canals, when conventional hearing aids with a mold in the ear cannot be used. The BAHA uses the ] as a pathway for sound to travel to the ]. For people with ], the BAHA bypasses the external ] and middle ear, stimulating the functioning cochlea. For people with ], the BAHA uses the skull to conduct the sound from the deaf side to the side with the functioning cochlea.

Individuals under the age of two (five in the USA) typically wear the BAHA device on a Softband. This can be worn from the age of one month as babies tend to tolerate this arrangement very well. When the child's skull bone is sufficiently thick, a ] "post" can be surgically embedded into the skull with a small ] exposed outside the skin. The BAHA sound processor sits on this abutment and ] sound ] to the external abutment of the titanium implant. The implant vibrates the skull and inner ear, which stimulate the ]s of the inner ear, allowing hearing.

The surgical procedure is simple both for the surgeon, involving very few risks for the experienced ear surgeon. For the patient, minimal discomfort and pain is reported. Patients may experience numbness of the area around the implant as small superficial nerves in the skin are sectioned during the procedure. This often disappears after some time. There is no risk of further hearing loss due to the surgery. One important feature of the BAHA is that, if a patient for whatever reason does not want to continue with the arrangement, it takes the surgeon less than a minute to remove it. The BAHA does not restrict the wearer from any activities such as outdoor life, sporting activities etc.

A BAHA can be connected to an FM system by attaching a miniaturized FM receiver to it.

Two main brands manufacture BAHAs today – the original inventors ], and the hearing aid company ].


===Eyeglass aids=== ===Eyeglass aids===
].<ref>{{Cite web |title=128.030 {{!}} Collections Online |url=https://collections.thackraymuseum.co.uk/object-128-030 |access-date=2024-09-23 |website=collections.thackraymuseum.co.uk}}</ref>]]
During the late 1950s through 1970s, before in-the-ear aids became common (and in an era when thick-rimmed eyeglasses were popular), people who wore both spectacles and hearing aids frequently chose a type of hearing aid that was built into the
temple pieces of the spectacles. However, the combination of glasses and hearing aids was inflexible: the range of frame styles was limited, and the user had to wear both hearing aids and glasses at once or wear neither. Today, most people who use both glasses and hearing aids simply use in-the-ear types. There still are some specialized situations where hearing aids built into the During the late 1950s through 1970s, before in-the-ear aids became common (and in an era when thick-rimmed ] were popular), people who wore both glasses and hearing aids frequently chose a type of hearing aid that was built into the
] pieces of the spectacles.<ref>{{cite web|title=Concealed Hearing Devices of the 20th Century|url=http://beckerexhibits.wustl.edu/did/20thcent/part6.htm|website=Concealed Hearing Devices of the 20th Century|publisher=Bernard Becker Medical Library|access-date=1 December 2014|url-status=live|archive-url=https://web.archive.org/web/20150123013026/http://beckerexhibits.wustl.edu/did/20thcent/part6.htm|archive-date=23 January 2015}}</ref> However, the combination of glasses and hearing aids was inflexible: the range of frame styles was limited, and the user had to wear both hearing aids and glasses at once or wear neither.<ref>{{Cite web|url=https://www.hearreview.com/why-dont-they-make-hearing-aid-glasses|title=Why Don't They Made Hearing Aids Glasses Anymore|website=www.hearreview.com|language=en|access-date=27 November 2018|archive-date=1 August 2020|archive-url=https://web.archive.org/web/20200801145002/https://www.hearreview.com/why-dont-they-make-hearing-aid-glasses|url-status=live}}</ref> Today, people who use both glasses and hearing aids can use in-the-ear types, or rest a BTE neatly alongside the arm of the glasses. There are still some specialized situations where hearing aids built into the frame of eyeglasses can be useful, such as when a person has hearing loss mainly in one ear: sound from a microphone on the "bad" side can be sent through the frame to the side with better hearing.
frame of eyeglasses can be useful, such as a person with hearing loss mainly in one ear: sound from a microphone on the "bad" side can be sent through the frame to the side with better hearing.


This can also be achieved by using ] or bi-CROS style hearing aids, which are now ] in sending sound to the better side.
Recently, a new type of eyeglass aid has been introduced by the Dutch company . The groundbreaking innovation employed by these 'hearing glasses' is the directional sensitivity of the hearing aid. Four microphones on each side of the frame work as two directional microphones which are able to discern between sound coming from the front and sound coming from the sides or back of the user. This allows for amplification of the sound coming from the front, the direction in which the user is looking, and suppression of sound coming from the sides or back.
Only very recently has the technology required become small enough, in size, to be put in the frame of the glasses.


====Spectacle hearing aids====
==Hearing Aid Technology==
These are generally worn by people with a hearing loss who either prefer a more cosmetic appeal of their hearing aids by being attached to their glasses or where sound cannot be passed in the normal way, via a hearing aids, perhaps due to a blockage in the ear canal. pathway or if the client experiences continual infections in the ear.
Spectacle aids come in two forms, ''bone conduction spectacles'' and ''air conduction spectacles''.

====Bone conduction spectacles====
Sounds are transmitted via a receiver attached from the arm of the spectacles which are fitted firmly behind the boney portion of the skull at the back of the ear, (mastoid process) by means of pressure, applied on the arm of the spectacles. The sound is passed from the receiver on the arm of the spectacles to the inner ear (cochlea), via the bony portion. The process of transmitting the sound through the bone requires a great amount of power. Bone conduction aids generally have a poorer high pitch response and are therefore best used for ''conductive hearing losses'' or where it is impractical to fit standard hearing aids.

====Air conduction spectacles====
Unlike the bone conduction spectacles the sound is transmitted via hearing aids which are attached to the arm or arms of the spectacles. When removing your glasses for cleaning, the hearing aids are detached at the same time. Whilst there are genuine instances where spectacle aids are a preferred choice, they may not always be the most practical option.

====Directional spectacles====
These 'hearing glasses' incorporate a directional microphone capability: four microphones on each side of the frame effectively work as two directional microphones, which are able to discern between sound coming from the front and sound coming from the sides or back of the user.<ref> {{webarchive|url=https://web.archive.org/web/20120415050021/http://www.aarpinternational.org/agingadvances_sub/agingadvances_sub_show.htm?doc_id=553940 |date=15 April 2012 }}, Publish Date: 1 March 2007, Related Company Website: www, varibel.nl. Accessed 10 February 2008.</ref> This improves the ] by allowing for amplification of the sound coming from the front, the direction in which the user is looking, and ] for sounds coming from the sides or behind.
Only very recently has the technology required become small enough to be fitted in the frame of the glasses. As a recent addition to the market, this new hearing aid is currently available only in the Netherlands and Belgium.<ref>The manufacturer's website is published in Dutch and French at {{cite web |url=http://varibel.nl/site/home/default.asp |title=Varibel.nl |access-date=9 February 2016 |archive-url=https://web.archive.org/web/20080222003941/http://varibel.nl/site/home/default.asp |archive-date=22 February 2008 }} and there is a TV news report in English at http://varibel.nl/site/Files/default.asp?iChannel=4&nChannel=Files </ref>

=== Stethoscope ===
These hearing aids are designed for ] with hearing loss who use ]s. The hearing aid is built into the speaker of the stethoscope, which amplifies the sound.

=== Hearing aid applications ===
]s (HAA) are software which, when installed on ], transforms them into hearing aids.<ref>{{Cite web|url=https://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/UCM263366.pdf|title=Mobile Medical Applications. Guidance for Industry and Food and Drug Administration Staff|year=2015|website=Food and Drug Administration|access-date=15 March 2019|archive-date=23 January 2019|archive-url=https://web.archive.org/web/20190123064529/https://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/UCM263366.pdf|url-status=live}}</ref>

The principle of HAA operation corresponds to the basic principles of operation of traditional hearing aids: the microphone receives an acoustic signal and converts it into a digital form. Sound amplification is achieved by the means of a mobile computational platform, in accordance with the degree and type of the user's ]. The processed audio signal is transformed into an audio signal and output to the user into the ]/]. Signal processing is implemented in ].

Constructional features of mobile computational platforms imply preferred use of stereo headsets with two speakers, which allows carrying out binaural hearing correction for the left and right ear separately.<ref name=":222">{{Cite journal|url=https://inf.grid.by/jour/article/view/149?locale=en_US|title=Hearing correction system based on mobile computing platform (in Russian)|journal=Informatics|author=E.S. Azarov |author2=M.I. Vashkevich |author3=S.V. Kozlova |author4=A.A. Petrovsky |volume=2|issue=42|year=2014|pages=5–24|issn=1816-0301|access-date=15 March 2019|archive-date=29 March 2019|archive-url=https://web.archive.org/web/20190329150406/https://inf.grid.by/jour/article/view/149?locale=en_US|url-status=live}}</ref> HAAs can work with both wired and wireless headsets and headphones.<ref name=":02">{{Cite book|title=Hearing aids|author=A. Vonlanthen |author2=H. Arndt |publisher=Feniks|year=2009|isbn=978-5-222-15490-8|location=Rostov-on-Don|language=ru|translator-last1=T |translator-first1=Gvelesiani}}</ref>

As a rule, HAAs have two operation modes: setup mode and hearing aid mode. Setup mode involves the user passing an ] procedure, which determines the user's hearing characteristics. Hearing aid mode is a hearing correction system that corrects the user's hearing in accordance with the user's ]. HAAs also incorporate background ] and ] suppression.<ref name=":222"/>

The user can independently choose a formula to enhance the sound, as well as adjust the level of the desired amplification to their wishes.<ref name=":02"/>

HAAs have several advantages (compared to traditional hearing aids):{{Citation needed|date=December 2021}}
* HAAs do not cause any psychological inconvenience;
* it is possible to achieve the highest sound pressure level and get high sound quality (due to large speakers and a long battery life);
* it is possible to use more complex audio ] algorithms and a higher ] (because of capacious battery);
* the possibility to implement more convenient application control functions for people with poor motor skills;
* resistance to ingress of earwax and moisture;
* software flexibility;
* the large distance between the microphone and the speaker prevents the occurrence of acoustic feedback;
* the set up of HAAs in simple cases does not require special equipment and qualifications;
* the user does not need to purchase and carry any separate device;
* various types of headphones and headsets can be used.

HAAs also have some disadvantages (compared to traditional hearing aids):
* because the microphone is not located in the ear, it does not use the functional advantages of the auricle and the natural acoustics of the outer ear.<ref name=":222"/>
* they are more noticeable and less comfortable to wear.

==Technology==
{{see also|History of hearing aids}}
The first electrical hearing aid used the ] of the telephone and was introduced in 1896. The ] made electronic amplification possible, but early versions of amplified hearing aids were too heavy to carry around. Miniaturization of vacuum tubes lead to portable models, and after World War II, wearable models using miniature tubes. The ] invented in 1948 was well suited to the hearing aid application due to low power and small size; hearing aids were an early adopter of transistors. The development of ]s allowed further improvement of the capabilities of wearable aids, including implementation of ] techniques and programmability for the individual user's needs.

===Compatibility with telephones===
]). Hearing aid users can use a telecoil (T) switch to hear announcements directly through their hearing aid receiver.]]
A hearing aid and a telephone are "compatible" when they can connect to each other in a way that produces clear, easily understood sound. The term "compatibility" is applied to all three types of telephones (wired, cordless, and mobile). There are two ways telephones and hearing aids can connect with each other:
* '''Acoustically:''' the ''sound'' from the phone's speaker is picked up by the hearing aid's microphone.
* '''Electromagnetically:''' the ''signal'' inside the phone's speaker is picked up by the hearing aid's "telecoil" or "T-coil", a special loop of wire inside the hearing aid.

Note that telecoil coupling has nothing to do with the radio signal in a cellular or cordless phone: the audio signal picked up by the telecoil is the weak electromagnetic field that is generated by the ] in the phone's speaker as it pushes the speaker cone back and forth.

The electromagnetic (telecoil) mode is usually more effective than the acoustic method. This is mainly because the microphone is often automatically switched off when the hearing aid is operating in telecoil mode, so background noise is not amplified. Since there is an electronic connection to the phone, the sound is clearer and distortion is less likely. But in order for this to work, the phone has to be hearing-aid compatible. More technically, the phone's speaker has to have a voice coil that generates a relatively strong electromagnetic field. Speakers with strong voice coils are more expensive and require more energy than the tiny ones used in many modern telephones; phones with the small low-power speakers cannot couple electromagnetically with the telecoil in the hearing aid, so the hearing aid must then switch to acoustic mode. Also, many mobile phones emit high levels of electromagnetic noise that creates audible static in the hearing aid when the telecoil is used. A workaround that resolves this issue on many mobile phones is to plug a wired (not Bluetooth) headset into the mobile phone; with the headset placed near the hearing aid the phone can be held far enough away to attenuate the static. Another method is to use a "neckloop" (which is like a portable, around-the-neck induction loop), and plug the neckloop directly into the standard audio jack (headphones jack) of a smartphone (or laptop, or stereo, etc.). Then, with the hearing aids' telecoil turned on (usually a button to press), the sound will travel directly from the phone, through the neckloop and into the hearing aids' telecoils.<ref name="T-coils and Smartphones">{{cite magazine|last=Mestayer|first=Kathi|title=Science is revealing how internal volume controls can influence our sensitivity to sound|url=https://view.publitas.com/p222-4764/hearing-health-winter-2013-issue/page/32|magazine=Hearing Health|access-date=17 August 2022|archive-date=17 August 2022|archive-url=https://web.archive.org/web/20220817044130/https://view.publitas.com/p222-4764/hearing-health-winter-2013-issue/page/32|url-status=live}}</ref>

On 21 March 2007, the ] issued the TIA-1083 standard,<ref> {{webarchive|url=https://web.archive.org/web/20120516084253/http://global.ihs.com/doc_detail.cfm?currency_code=USD&customer_id=2125422C4E0A&oshid=2125422C4D0A&shopping_cart_id=292558332C4A2020495A4D3B200A&country_code=US&lang_code=ENGL&item_s_key=00492018&item_key_date=890114&input_doc_number=TIA-1083&input_doc_title= |date=16 May 2012 }}. ihs.com</ref> which gives manufacturers of cordless telephones the ability to test their products for compatibility with most hearing aids that have a T-Coil magnetic coupling mode. With this testing, digital cordless phone manufacturers will be able to inform consumers about which products will work with their hearing aids.<ref>{{cite web|url=http://www.tiaonline.org/news_events/press_room/press_releases/2007/press-1175779463784.cfm |access-date=3 November 2011 |archive-url=https://web.archive.org/web/20101206172236/http://www.tiaonline.org/news_events/press_room/press_releases/2007/press-1175779463784.cfm |archive-date=6 December 2010 |title=New TIA Standard Will Improve Hearing Aid Compatibility with Digital Cordless Phones|date=5 April 2007|publisher=U.S. Telecommunications Industry Association}}</ref>

The ] (ANSI) has a ratings scale for compatibility between hearing aids and phones:
* When operating in acoustic ('''M'''icrophone) mode, the ratings are from M1 (worst) to M4 (best).
* When operating in electromagnetic ('''T'''elecoil) mode, the ratings are from T1 (worst) to T4 (best).

The best possible rating is M4/T4 meaning that the phone works well in both modes. Devices rated below M3 are unsatisfactory for people with hearing aids.

Computer programs that allow the creation of a hearing aid using a PC, tablet or smartphone are currently gaining in popularity.<ref name="gluxix">{{cite web |url=http://www.gluxix.net/deafnews/sobitiya/4617-2014-03-13-19-08-50 |title=Приложение для смартфонов заменит глухим слуховой аппарат? – Глухих.нет. Новостной портал для глухих и слабослышащих &#124; Новости мира глухих и слабослышащих &#124; Сайт глухих &#124; Спорт глухих &#124; Can application substitute hearing aid? |publisher=gluxix.net |access-date=18 February 2015 |date=13 March 2014 |archive-date=25 December 2014 |archive-url=https://web.archive.org/web/20141225103754/http://www.gluxix.net/deafnews/sobitiya/4617-2014-03-13-19-08-50 |url-status=live }}</ref> Modern mobile devices have all the necessary components to implement this: hardware (an ordinary microphone and headphones may be used) and a high-performance microprocessor that carries digital sound processing according to a given algorithm.
Application configuration is carried out by the user themselves in accordance with the individual features of their hearing ability. The computational power of modern mobile devices is sufficient to produce the best sound quality. This, coupled with software application settings (for example, profile selection according to a sound environment) provides for high comfort and convenience of use.
In comparison with the digital hearing aid, mobile applications have the following advantages:
* acoustic gain is up to 30&nbsp;dB (with a standard headset);
* complete invisibility (smartphone is not associated with a hearing aid);
* ease of use (no need to use additional devices, batteries and so on.);
* Fast switching between the external headset and phone microphone;
* free distribution of applications.
* High duration of the battery;
* high sampling frequency (44.1&nbsp;kHz) providing for excellent sound quality;
* high wearing comfort;
* low delay in audio processing (from 6,3 to 15,7 ms – depending on the mobile device model);
* No loss of settings when switching from one gadget to another and back again;
* No need to get used to it, when changing mobile devices;
* user-friendly interface of software settings;
It should be clearly understood that "hearing aid" application for smartphone / tablet cannot be considered a complete substitution of a digital hearing aid, since the latter:
* is a medical device (exposed to the relevant procedures of testing and certification);
* is adjusted using ] procedures.<ref name="fda">{{cite web |url=https://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ConnectedHealth/MobileMedicalApplications/default.htm#b |title=Mobile Medical Applications |publisher=fda.gov |access-date=18 February 2015 |archive-date=2 May 2013 |archive-url=https://web.archive.org/web/20130502045050/https://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ConnectedHealth/MobileMedicalApplications/default.htm#b |url-status=live }}</ref>
* is designed for use by doctor's prescription;
Functionality of hearing aid applications may involve a hearing test (]) too. However, the results of the test are used only to adjust the device for comfortable working with the application. The procedure of hearing testing in any way cannot claim to replace an audiometry test carried out by a medical specialist, so cannot be a basis for diagnosis.
* Apps such as Oticon ON for certain ] (Apple) and ] can assist in locating a lost/misplaced hearing aid.<ref>{{cite web |url=http://www.oticon.global/solutions/accessories/connectivity |title=Hearing aids, information on hearing loss and tinnitus &#124; Oticon |website=www.oticon.global |access-date=25 September 2016 |archive-date=27 September 2016 |archive-url=https://web.archive.org/web/20160927063331/http://www.oticon.global/solutions/accessories/connectivity |url-status=live }}</ref>


===Wireless=== ===Wireless===
Recent hearing aids include wireless hearing aids. One hearing aid can transmit to the other side so that pressing one aid's program button simultaneously changes the other aid, so that both aids change background settings simultaneously. FM listening systems are now emerging with wireless receivers integrated with the use of hearing aids. A separate wireless microphone can be given to a partner to wear in a restaurant, in the car, during leisure time, in the shopping mall, at lectures, or during religious services. The voice is transmitted wirelessly to the hearing aids eliminating the effects of distance and ]. FM systems have shown to give the best speech understanding in noise of all available technologies.
]
FM systems can also be hooked up to a TV or a stereo.
Recent hearing aids include wireless hearing aids. One hearing aid can transmit to the other side so that pressing one aid's program button simultaneously changes the other aid and both aids change background settings simultaneously. FM (receiving) hearing aids are also now emerging with inbuilt wireless receivers. A separate wireless microphone can be given to a partner to wear in a restaurant, in the car or in another room. The voice is transmitted wirelessly to the hearing aids reducing the effects of distance and ].


2.4 gigahertz Bluetooth connectivity is the most recent innovation in wireless interfacing for hearing instruments to audio sources such as TV streamers or Bluetooth enabled mobile phones. Current hearing aids generally do not stream directly via Bluetooth but rather do so through a secondary streaming device (usually worn around the neck or in a pocket), this bluetooth enabled secondary device then streams wirelessly to the hearing aid but can only do so over a short distance. This technology can be applied to ready-to-wear devices (BTE, Mini BTE, RIE, etc.) or to custom made devices that fit directly into the ear.<ref>{{cite web|last1=Mroz|first1=Mandy|title=Hearing Aids and Bluetooth Technology|url=http://www.healthyhearing.com/help/hearing-aids/bluetooth|website=Hearing Aids and Bluetooth Technology|publisher=Healthy Hearing|access-date=1 December 2014|url-status=live|archive-url=https://web.archive.org/web/20141109041954/http://www.healthyhearing.com/help/hearing-aids/bluetooth|archive-date=9 November 2014}}</ref>
Many theatres and lecture halls are now equipped with ]s that transmit the sound directly from the stage; audience members can borrow suitable receivers and hear the program without background noise.
<gallery class="center">
File:Oticon Bluetooth hearing aids.jpg|] hearing aids for use with ] wireless devices
File:فوناك.jpg|] wireless FM system
</gallery>


In developed countries FM systems are considered a cornerstone in the treatment of hearing loss in children. More and more adults discover the benefits of wireless FM systems as well, especially since transmitters with different microphone settings and ] for wireless cell phone communication have become available.<ref>{{cite journal|author1=Dave Fabry |author2=Hans Mülder |author3=Evert Dijkstra |date=November 2007|title= Acceptance of the wireless microphone as a hearing aid accessory for adults|journal= The Hearing Journal|volume= 60 | issue = 11|pages= 32–36|doi=10.1097/01.hj.0000299170.11367.24|s2cid=168059640 |doi-access=free}}</ref>
===Directional microphones===
Many hearing aids now have directional microphones, which can be a major improvement
in crowded places such as restaurants and open-plan offices, because the directional
microphone allows the user to focus on whoever is directly in front with reduced
interference from conversations behind and to the sides. It is common for such a
hearing aid to have both a directional microphone and an omnidirectional microphone
and a switch that lets the user choose between hearing in all directions versus
hearing only in the direction his or her head is facing. Some more-advanced models
can electronically subtract signals so the user hears the directional signal minus
the omnidirectional signal for improved background noise rejection.


Many theatres and ] are now equipped with ]s that transmit the sound directly from the stage; ] members can borrow suitable receivers and hear the program without background noise. In some theatres and churches FM transmitters are available that work with the personal FM receivers of hearing instruments.
The recently introduced eyeglass aid by the Dutch company Varibel uses four microphones on each side of the frame of a pair of glasses that, together, work as two directional microphones. Technology inside the frame is able to discern between sounds coming from the front and sounds coming from the sides or back, amplifying the sound which is coming from the direction in which the user looks, suppressing other sounds.

===Directional microphone===
Most older hearing aids have only an omnidirectional microphone. An omnidirectional microphone amplifies sounds equally from all directions. In contrast, a directional microphone amplifies sounds from one direction more than sounds from other directions. This means that sounds originating from the direction the system is steered toward are amplified more than sounds coming from other directions. If the desired speech arrives from the direction of steering and the noise is from a different direction, then compared to an omnidirectional microphone, a directional microphone provides a better ]. Improving the signal-to-noise ratio improves speech understanding in noise. Directional microphones have been found to be the second best method to improve the signal-to-noise ratio (the best method was an FM system, which locates the microphone near the mouth of the desired talker).<ref>{{cite journal | vauthors = Hawkins DB | date = November 1984 | title = Comparisons of speech recognition in noise by mildly-to-moderately hearing-impaired children using hearing aids and FM systems | journal = Journal of Speech and Hearing Disorders | volume = 49 | issue = 4| pages = 409–18 | doi=10.1044/jshd.4904.409| pmid = 6503247 }}</ref>

Many hearing aids have both an omnidirectional and a directional microphone mode.{{citation needed|date=August 2022}} This is because the wearer may not need or desire the noise-reducing properties of the directional microphone in a given situation.{{citation needed|date=August 2022}} Typically, the omnidirectional microphone mode is used in quiet listening situations (e.g. living room) whereas the directional microphone is used in noisy listening situations (e.g. restaurant).{{citation needed|date=August 2022}} The microphone mode is typically selected manually by the wearer.{{citation needed|date=August 2022}} Some hearing aids automatically switch the microphone mode.{{citation needed|date=August 2022}}

] directional microphones automatically vary the direction of maximum amplification or rejection (to reduce an interfering directional sound source). The direction of amplification or rejection is varied by the hearing aid processor. The processor attempts to provide maximum amplification in the direction of the desired speech signal source or rejection in the direction of the interfering signal source. Unless the user manually temporarily switches to a "restaurant program, forward only mode" adaptive directional microphones frequently amplify the speech of other talkers in a cocktail party type environments, such as restaurants or coffee shops; this can also be helpful during business meetings. The presence of multiple speech signals makes it difficult for the processor to correctly select the desired speech signal. Another disadvantage is that some noises often contain characteristics similar to speech, making it difficult for the hearing aid processor to distinguish the speech from the noise. Despite the disadvantages, adaptive directional microphones can provide improved speech recognition in noise.<ref>{{cite journal | vauthors = Ricketts T, Henry P | date = March 2002 | title = Evaluation of an adaptive, directional-microphone hearing aid | journal = International Journal of Audiology | volume = 41 | issue = 2| pages = 100–112 | doi=10.3109/14992020209090400|pmid=12212855 |s2cid=2035086 }}</ref>

FM systems have been found to provide a better signal-to-noise ratio even at larger speaker-to-talker distances in simulated testing conditions.<ref>{{cite journal |date= June 2004 |title= Speech perception in noise: directional microphones versus frequency modulation (FM) systems |journal= Journal of the American Academy of Audiology |volume= 15 |issue= 6 |pages= 426–439 |doi= 10.3766/jaaa.15.6.4 |pmid= 15341224 |vauthors= Lewis MS, Crandell CC, Valente M, Horn JE |url= https://digitalcommons.wustl.edu/audio_hapubs/5 |access-date= 17 August 2022 |archive-date= 27 November 2022 |archive-url= https://web.archive.org/web/20221127084845/https://digitalcommons.wustl.edu/audio_hapubs/5/ |url-status= live }}</ref>


===Telecoil=== ===Telecoil===
{{main|Audio induction loop}}
Telecoils (T-coils) allow different sound sources to be directly connected to the hearing aid, improving sound quality and allowing the hearing aid wearer to easily perceive the signal of interest in almost any environment, and regardless of background noise. They can be used with ]s, FM systems, induction loop systems and public address systems.
Telecoils or T-coils (from "Telephone Coils") are small devices installed in hearing aids or cochlear implants. An ] generates an electromagnetic field that can be detected by T-coils, allowing audio sources to be directly connected to a hearing aid. The T-coil is intended to help the wearer filter out background noise. They can be used with telephones, FM systems (with neck loops), and induction loop systems (also called "hearing loops") that transmit sound to hearing aids from public address systems and TVs. In the UK and the Nordic countries, hearing loops are widely used in churches, shops, railway stations, and other public places. In the US, telecoils and hearing loops are gradually becoming more common. Audio induction loops, telecoils and hearing loops are gradually becoming more common also in ].


T-coils are comprised of a metal core (or rod) around which ultra-fine wire is coiled. T-coils are also called induction coils because when the coil is placed in an ] (EM) field, an alternating electrical current is induced in the wire (Ross, 2002b; Ross, 2004). The T-coil detects EM energy and transduces (or converts) it to ]. T-coils can also be used to pick up ] signals, just as a ] picks up an acoustic signal; the T-coil then sends the signal to the hearing aid circuit or processor for amplification. A T-coil consists of a metal core (or rod) around which ultra-fine wire is coiled. T-coils are also called induction coils because when the coil is placed in a magnetic field, an alternating electric current is induced in the wire (Ross, 2002b; Ross, 2004). The T-coil detects magnetic energy and transduces (converts) it to electrical energy. In the United States, the ]'s TIA-1083 standard, specifies how analog handsets can interact with telecoil devices, to ensure the optimal performance.<ref> {{webarchive|url=https://web.archive.org/web/20120425143707/http://ftp.tiaonline.org/UPED/20070717/UPED-20070717-010_TIA-1083_Flyer.pdf |date=25 April 2012 }}. U.S. Telecommunications Industry Association</ref>


Although T-coils are effectively a wide-band receiver, interference is unusual in most hearing loop situations. Interference can manifest as a buzzing sound, which varies in volume depending on the distance the wearer is from the source. Sources are electromagnetic fields, such as CRT computer monitors, older fluorescent lighting, some dimmer switches, many household electrical appliances and airplanes.
DAI-direct audio input allows the hearing aid to be connected to an external audio source like a CD player or an assistive listening device (ALD). This is preferred by many users, as opposed to using a T-coil with a standard set of headphones, as there is less interference (usually heard as a buzzing noise).

The states of Florida and Arizona have passed legislation that requires hearing professionals to inform patients about the usefulness of telecoils.

====Legislation affecting use====
In the United States, the Hearing Aid Compatibility Act of 1988 requires that the ] (FCC) ensure that all telephones manufactured or imported for use in the United States after August 1989, and all "essential" telephones, be hearing aid-compatible (through the use of a telecoil).<ref>{{cite web|url=http://pratp.upr.edu/informacion/politica-publica/leyes-y-reglamentos/leyes-federales/public-law-100-394-aug.-16-1988-hearing-aid|title=Public Law 100-394, – Hearing Aid Compatibility Act of 1988|publisher=PRATP|access-date=8 June 2013|url-status=live|archive-url=https://web.archive.org/web/20100726190853/http://pratp.upr.edu/informacion/politica-publica/leyes-y-reglamentos/leyes-federales/public-law-100-394-aug.-16-1988-hearing-aid|archive-date=26 July 2010}}</ref>

"Essential" phones are defined as "coin-operated telephones, telephones provided for emergency use, and other telephones frequently needed for use by persons using such hearing aids." These might include workplace telephones, telephones in confined settings (like hospitals and nursing homes), and telephones in hotel and motel rooms. Secure telephones, as well as telephones used with public mobile and private radio services, are exempt from the HAC Act. "Secure" phones are defined as "telephones that are approved by the U.S. Government for the transmission of classified or sensitive voice communications."

In 2003, the FCC adopted rules to make ] wireless telephones compatible with hearing aids and ]s. Although analog wireless phones do not usually cause interference with hearing aids or cochlear implants, digital wireless phones often do because of electromagnetic energy emitted by the phone's ], ], or other components. The FCC has set a timetable for the development and sale of digital wireless telephones that are compatible with hearing aids. This effort promises to increase the number of digital wireless telephones that are hearing aid-compatible. Older generations of both ] and ] phones used analog technology.

===Audio boot===
]
An '''audio boot''' or '''audio shoe''' is an electronic device used with hearing aids; hearing aids often come with a special set of metal contacts for audio input. Typically the audio boot will fit around the end of the hearing aid (a behind-the-ear model, as in-the-ear do not afford any purchase for the connection) to link it with another device, like an FM system or a cellphone or even a digital audio player.<ref>{{Cite web|url=http://www.nchearingloss.org/boot.htm?fromncshhh|title=Boot Definition|website=www.nchearingloss.org|access-date=2 June 2017|archive-date=3 March 2016|archive-url=https://web.archive.org/web/20160303190506/http://www.nchearingloss.org/boot.htm?fromncshhh|url-status=live}}</ref>

===Direct audio input===
]
Direct audio input (DAI) allows the hearing aid to be directly connected to an external audio source like a CD player or an assistive listening device (ALD). By its very nature, DAI is susceptible to far less electromagnetic interference, and yields a better quality audio signal as opposed to using a T-coil with standard ]. An ] is a type of device that may be used to facilitate DAI.<ref>{{Cite web|url=http://www.nchearingloss.org/boot.htm?fromncshhh|title=Boot Definition|website=www.nchearingloss.org|access-date=2 June 2017|url-status=live|archive-url=https://web.archive.org/web/20160303190506/http://www.nchearingloss.org/boot.htm?fromncshhh|archive-date=3 March 2016}}</ref>


===Processing=== ===Processing===
Every electronic hearing aid has at minimum a microphone, a loudspeaker (commonly called a receiver), a battery, and electronic circuitry. The electronic circuitry varies among devices, even if they are the same style. The circuitry falls into three categories based on the type of audio processing (analog or digital) and the type of control circuitry (adjustable or programmable). Hearing aid devices generally do not contain processors strong enough to process complex ] for sound source localization.<ref>{{cite book|author=Ganguly Anshuman, Reddy Chandan, Hao Yiya, Panahi Issa|title=2016 IEEE International Workshop on Signal Processing Systems (SiPS)|year=2016|isbn=978-1-5090-3361-4|pages=165–170|chapter=Improving Sound Localization for Hearing Aid Devices Using Smartphone Assisted Technology|doi=10.1109/SiPS.2016.37|s2cid=7603815}}</ref>
The inside mechanisms of hearing aids vary among devices, even if they are the same style. Three types of circuitry, or electronics, are used:


====Analog====
* ]/Adjustable: The hearing professional (], ], ], or ]) determines the volume and other specifications required for the patient's hearing aid, and then a laboratory builds the aid to meet those specifications. The hearing professional retains some flexibility to make adjustments. This type of circuitry is generally the least expensive.
] audio may have:
* Adjustable control: The audio circuit is analog with electronic components that can be adjusted. The hearing professional determines the gain and other specifications required for the wearer, and then adjusts the analog components either with small controls on the hearing aid itself or by having a laboratory build the hearing aid to meet those specifications. After the adjustment the resulting audio does not change any further, other than overall loudness that the wearer adjusts with a volume control. This type of circuitry is generally the least flexible. The first practical electronic hearing aid with adjustable analog audio circuitry was based on US Patent 2,017,358, "Hearing Aid Apparatus and Amplifier" by Samual Gordon Taylor, filed in 1932.
* Programmable control: The audio circuit is analog but with additional electronic control circuitry that can be programmed by an audiologist, often with more than one program.<ref>{{cite web|url=http://www.livestrong.com/article/252221-analog-vs-digital-hearing-aids/|title=Analog Vs. Digital Hearing Aids|last=Heidtman|first=Laurel|date=28 September 2010|publisher=LiveStrong.com|access-date=23 July 2012|url-status=live|archive-url=https://web.archive.org/web/20120503011143/http://www.livestrong.com/article/252221-analog-vs-digital-hearing-aids/|archive-date=3 May 2012}}</ref> The electronic control circuitry can be fixed during manufacturing or in some cases, the hearing professional can use an external computer temporarily connected to the hearing aid to program the additional control circuitry. The wearer can change the program for different listening environments by pressing buttons either on the device itself or on a remote control or in some cases the additional control circuitry operates automatically. This type of circuitry is generally more flexible than simple adjustable controls. The first hearing aid with analog audio circuitry and automatic digital electronic control circuitry was based on US Patent 4,025,721, "Method of and means for adaptively filtering near-stationary noise from speech" by D Graupe, GD Causey, filed in 1975. This digital electronic control circuitry was used to identify and automatically reduce noise in individual frequency channels of the analog audio circuits and was known as the Zeta Noise Blocker.


====Digital====
* Analog/Programmable: The hearing professional uses a computer to program the hearing aid. The circuitry of analog/programmable hearing aids will accommodate more than one program or setting. If the aid is equipped with a remote control device, the wearer can change the program to accommodate a given listening environment. Analog/programmable circuitry can be used in all types of hearing aids.
]
] audio, programmable control: Both the audio circuit and the additional control circuits are fully digital. The hearing professional programs the hearing aid with an external computer temporarily connected to the device and can adjust all processing characteristics on an individual basis. Fully digital circuitry allows implementation of many additional features not possible with analog circuitry, can be used in all styles of hearing aids and is the most flexible; for example, digital hearing aids can be programmed to amplify certain frequencies more than others, and can provide better sound quality than analog hearing aids. Fully digital hearing aids can be programmed with multiple programs that can be invoked by the wearer, or that operate automatically and adaptively. These programs reduce acoustic feedback (whistling), reduce background noise, detect and automatically accommodate different listening environments (loud vs. soft, speech vs. music, quiet vs. noisy, etc.), control additional components such as multiple microphones to improve spatial hearing, transpose frequencies (shift high frequencies that a wearer may not hear to lower frequency regions where hearing may be better), and implement many other features. Fully digital circuitry also allows control over wireless transmission capability for both the audio and the control circuitry. Control signals in a hearing aid on one ear can be sent wirelessly to the control circuitry in the hearing aid on the opposite ear to ensure that the audio in both ears is either matched directly or that the audio contains intentional differences that mimic the differences in normal binaural hearing to preserve spatial hearing ability. Audio signals can be sent wirelessly to and from external devices through a separate module, often a small device worn like a pendant and commonly called a "streamer", that allows wireless connection to yet other external devices. This capability allows optimal use of mobile telephones, personal music players, remote microphones and other devices. With the addition of speech recognition and internet capability in the mobile phone, the wearer has optimal communication ability in many more situations than with hearing aids alone. This growing list includes voice activated dialing, voice activated software applications either on the phone or on the internet, receipt of audio signals from databases on the phone or on internet, or audio signals from television sets or from global positioning systems. The first practical, wearable, fully digital hearing aid was invented by Maynard Engebretson, Robert E Morley Jr. and Gerald R Popelka.<ref>{{cite web|url=http://www.asha.org/Publications/leader/2007/071226/f071226c.htm|archive-url=https://archive.today/20120717222846/http://www.asha.org/Publications/leader/2007/071226/f071226c.htm|archive-date=17 July 2012|title=Digital Hearing Aids|last=Levitt|first=Harry|date=26 December 2007|publisher=The ASHA Leader|access-date=23 July 2012}}</ref> Their work resulted in ] 4,548,082, "Hearing aids, signal supplying apparatus, systems for compensating hearing deficiencies, and methods" by A Maynard Engebretson, Robert E Morley Jr. and Gerald R Popelka, filed in 1984. This patent formed the basis of all subsequent fully digital hearing aids from all manufacturers, including those produced currently.<ref>{{Cite web|url=http://www.himpp.info/about-himpp/himpp-history/|title=HIMPP History &#124; HIMPP|access-date=24 December 2021|archive-date=24 December 2021|archive-url=https://web.archive.org/web/20211224163458/http://www.himpp.info/about-himpp/himpp-history/|url-status=live}}</ref>


The signal processing is performed by the microprocessor in real time and taking into account the individual preferences of the user (for example, increasing bass for better speech perception in noisy environments, or selective amplification of high frequencies for people with reduced sensibility to this range). The microprocessor automatically analyzes the nature of the external background noise and adapts the signal processing to the specific conditions (as well as to its change, for example, when the user goes outside from the building).<ref name="radugazvukov">{{cite web|url=http://www.radugazvukov.ru/information/articles/detail.php?article=3371|title=Как работают слуховые аппараты|publisher=radugazvukov.ru|access-date=18 February 2015|archive-url=https://web.archive.org/web/20141225213446/http://www.radugazvukov.ru/information/articles/detail.php?article=3371|archive-date=25 December 2014}}</ref>
* ]/Programmable: The hearing professional programs the hearing aid with a computer and can adjust the sound quality and response time on an individual basis. Digital hearing aids use a microphone, receiver, battery, and computer chip. Digital circuitry provides the most flexibility for the hearing professional to make adjustments for the hearing aid. Digital circuitry can be used in all types of hearing aids and is typically the most expensive. However, digital hearing aids can be specially programmed with multiple programs for quiet situations, background noise reduction, music listening, and directionality. Many also have more powerful feedback-reduction and/or cancellation technology.


In ], for example using neural networks, finds application in hearing aids. Problems may arise if these methods filter out emergency sounds such as fire alarms and car horns.<ref>{{Cite conference |author=Soha A. Nossier, Julie Wall1, Mansour Moniri, Cornelius Glackin, Nigel Cannings |title=Convolutional Recurrent Smart Speech Enhancement Architecture for Hearing Aids |conference=Interspeech 2022 |location=Incheon, Korea |date=18-22 September 2022 |url=https://www.isca-speech.org/archive/pdfs/interspeech_2022/nossier22_interspeech.pdf |access-date=20 November 2022 |archive-date=20 November 2022 |archive-url=https://web.archive.org/web/20221120114904/https://www.isca-speech.org/archive/pdfs/interspeech_2022/nossier22_interspeech.pdf |url-status=live }}</ref>
==Adjustment to Hearing Aids==


==== Difference between digital and analog hearing aids ====
For the majority of users, hearing aids will not completely restore or fix hearing loss; they are an ''aid'' to make sounds accessible to those who have hearing loss. Two problems occur with hearing loss that cannot be assisted by hearing aids:
Analogue hearing aids make all the sounds picked up by the microphone louder. For example, speech and ambient noise will be made louder together. On the other hand, digital hearing aid (DHA) technology processes the sound using digital technology. Before transmitting the sound to the speaker, the DHA microprocessor processes the digital signal received by the microphone according to an algorithm. This allows certain-frequency sounds to be made louder according to the individual user's settings (personal audiogram), and the DHA can automatically adjust to various environments (noisy streets, quiet room, concert hall, etc.).
* When the auditory cortex of the brain does not receive input/stimulation (i.e. what happens in hearing loss), this part of the brain may start to lose cells, and the ability to process sound. This is most common with more severe hearing losses, and cannot be reversed with hearing aids. Although this cell loss is worse in severe hearing loss, it is seen in all amounts of hearing loss and is caused by sensory deprivation.
* Damage to the hair cells of the inner ear result in sensorineural hearing loss. When these hair cells are damaged, a person loses some ability to discriminate between sounds. This will likely cause decreased ability to understand speech. In this case, amplifying speech (as a hearing aid does) does not always improve speech understanding.


For users with varying degrees of hearing loss, it is difficult to perceive the entire frequency range of external sounds. DHAs with multi-channel digital processing allow a user to "compose" the output sound by fitting a whole spectrum of the input signal into it. This gives users with limited hearing abilities the opportunity to perceive the whole range of ambient sounds, despite the personal difficulties of perception of certain frequencies. Moreover, even in this "narrow" range the DHA microprocessor is able to emphasize desired sounds (e.g. speech), lowering unwanted loud, high, etc., sounds at the same time.
Multiple follow-up visits are common, particularly for new hearing aid users. The most common complaint about hearing aids, especially when someone starts wearing them for the first time, is that the sound of their own voice is too loud or that it sounds like they are talking into a barrel. Most hearing aid users will adjust to the sound of their own voices within several months if the aids are worn regularly. If the problem persists, ask your dispenser or audiologist if any adjustments can be made to the hearing aid.


According to research<ref name="karenscottaudiology">{{cite journal|url=http://karenscottaudiology.com/wp-content/uploads/2010/07/Satisfaction_Digital_Hearing_Aids_MarkeTrak.pdf|date=21 December 2009|title=HJ0905 Kochkin copy|author=Janet McCaffrey|journal=The Hearing Journal|access-date=18 February 2015|archive-url=https://web.archive.org/web/20160304024808/http://karenscottaudiology.com/wp-content/uploads/2010/07/Satisfaction_Digital_Hearing_Aids_MarkeTrak.pdf|archive-date=4 March 2016}}</ref> DHAs have a number of significant advantages compared to ] hearing aids:
==Hearing aid sales==
* "Self-learning" and adaptive adjustment. They can implement adaptive selection of amplification parameters and processing.
* Effective acoustic feedback reduction. The acoustic whistling common to all hearing aids can be adaptively controlled.
* Effective use of directional microphones. Directional microphones can be adaptively controlled.
* Extended frequency range. A larger range of frequencies can be implemented with frequency shifting.
* Flexibility in selective amplification. They can provide more flexibility in frequency specific amplification to match the individual hearing characteristics of the user.
* Improved connection to other devices. Connection to other devices such as smartphones and televisions is possible.
* Noise reduction. They can reduce the background noise level to increase user comfort in noisy environments.
* Speech recognition. They can distinguish the speech signal from the overall spectrum of sounds, which facilitates speech perception.


These advantages of DHAs were confirmed by a number of studies<ref name="hearingreview">{{cite web|url=http://www.hearingreview.com/2003/10/fitting-tips-essentials-of-hearing-aid-selection-part-1-cosmetics-are-not-just-what-meets-the-ear/|title=Fitting Tips: Essentials of Hearing Aid Selection, Part 1: Cosmetics Are Not Just What Meets the Ear – Hearing Review|date=2 October 2003|publisher=hearingreview.com|access-date=18 February 2015|archive-date=18 February 2015|archive-url=https://web.archive.org/web/20150218180919/http://www.hearingreview.com/2003/10/fitting-tips-essentials-of-hearing-aid-selection-part-1-cosmetics-are-not-just-what-meets-the-ear/|url-status=live}}</ref><ref name="phonak2">{{cite web|url=http://www.phonak.com/content/dam/phonak/b2b/Events/conference_proceedings/adult_conference_chicago_2006/monday/2006proceedings_pichorafuller.pdf|date=8 August 2007|title=24_P54090_Pho_Kapitel_06bis07|author=Richard Preid Fotorotar AG|access-date=18 February 2015|archive-url=https://web.archive.org/web/20150218165213/http://www.phonak.com/content/dam/phonak/b2b/Events/conference_proceedings/adult_conference_chicago_2006/monday/2006proceedings_pichorafuller.pdf|archive-date=18 February 2015}}</ref><ref name="hearingreview2">{{cite web|url=http://www.hearingreview.com/2005/12/hearing-review-three-year-index-2003-2005/|title=Hearing Review Three-Year Index 2003–2005 – Hearing Review|date=6 December 2005|publisher=hearingreview.com|access-date=18 February 2015|archive-date=18 February 2015|archive-url=https://web.archive.org/web/20150218180822/http://www.hearingreview.com/2005/12/hearing-review-three-year-index-2003-2005/|url-status=live}}</ref> relating to the comparative analysis of digital hearing aids of second and first generations and analog hearing aids.
Hearing aids are often advertised at widely varying prices, from $300 US to $5,000 US per hearing aid. A major factor contributing to the wide variance in price is the number and complexity of hearing aids available. Comparison shopping is very difficult for anyone who has not studied hearing and sound sciences. Another factor in the variance of prices is the bundling of services needed to customize a hearing aid to a specific ear and hearing loss. The complexity of these devices, the amount of customization required, and the personal nature of hearing suggest the best place to buy a hearing aid is somewhere you are comfortable, from someone you trust.


==== Difference between digital hearing aids and hearing aid applications ====
Buyers of hearing aids will commonly seek the expert advice of ] or ]s. Audiologists will have specially calibrated equipment and sound proof booths to conduct comprehensive ]s to describe a hearing loss. Many ] work in conjunction with an ], though some have independent practices.
]s have all the necessary hardware to perform the functions of a digital hearing aid: microphone, AD converter, digital processor, DA converter, amplifier, and speakers. External microphone and speakers can also be connected as a special headset.


The operational principles of hearing aid applications correspond to general operational principles of digital hearing aids: the microphone perceives an acoustic signal and converts it to digital form. Sound amplification is achieved through hardware and software in accordance with the user's hearing characteristics. Then, the signal is converted to analog form and received in the headphones by the user. The signal is processed in real time.
In the United States, Hearing aid dispensers (Hearing Instrument Specialists) also sell hearing aids. Hearing Instrument Specialists are professionals with at least a high school diploma and 2 years of training/apprenticeship in hearing aid sales.


Stereo headsets with two speakers can be used, which allows separate binaural hearing correction for the left and right ear.<ref name=":222"/>
In addition to the results of a hearing test, which describe a hearing loss, a recommendation for a specific amplification instrument should consider a person's listening lifestyle. Many features available in hearing aids (multiple and directional microphones, noise reduction strategies, "programs", etc.) represent strategies to address specific situations. Overloading on features that are not useful to the individual unnecessarily increases the cost and complexity of a hearing aid.


Unlike digital hearing aids, the adjustment of hearing aid applications is an integral part of the application itself.<ref name=":02"/> Hearing aid applications are adjusted in accordance with the user's ]. The whole adjustment process is automated so that the user can perform ] on their own.
Another consideration for determining the optimal hearing aid is physical and mental dexterity. Many hearing aids offer special features, such as different "programs". However, if someone lacks the physical dexterity to manipulate small controls, or does not have the presence of mind to keep track of which "program" is running, these nice features can make the instrument less effective since it may often be operating in a mode that is inappropriate for the situation.


The hearing correction application has two modes: audiometry and correction. In the audiometry mode, hearing thresholds are measured. In the correction mode, the signal is processed with respect to the obtained thresholds.
Finally, there are also personal concerns such as cost and the visibility of the hearing aid. Hearing aids are typically not covered, or only partially covered, by most insurance plans in the United States. As a result, they represent a considerably sized purchase for most consumers. The visibility of a hearing aid to others is important to some people. There is often a stigma associated with large visible amplification instruments, such as BTEs, so many people prefer hearing aid that are discreet.


Hearing aid applications also provide for different computational formulas for the calculation of sound amplification based on the audiometry data. These formulas are intended for maximum comfortable speech amplification and best sound intelligibility.


Hearing aid applications allow the user to save different user profiles for different acoustic environments. Thus, in contrast to the static settings of digital hearing aids, the user can quickly switch between the profiles depending on the acoustic environment.

One of the most important characteristics of the hearing aid is acoustic feedback. In hearing aid applications, there is a significant hardware delay, so hearing aid applications use a signal processing scheme with the minimum possible algorithmic delay to make it as short as possible.<ref name=":222" />

== Difference between PSAP and digital hearing aids ==
] (PSAP) are classified by the FDA as "personal sound amplification devices". These compact electronic devices are designed for people without hearing loss. Unlike hearing aids (which the FDA classifies as devices to compensate for hearing impairment),<ref name="samag">{{cite web|title=Применение технологии широкополосного изменения огибающей спектра звукового сигнала Petralex® в онлайн-приложениях коррекции слуха::Журнал СА 7–8.2014 (Mann, Eric A., M.D., PhD, "Hearing Aids and Personal Sound Amplifiers: Know the Difference", U.S. Food and Drug Administration Consumer Updates website, Oct. 20, 2009. Retrieved 2013-05-23.)|url=http://samag.ru/archive/article/2759|url-status=live|access-date=18 February 2015|publisher=samag.ru|language=ru|archive-date=25 December 2014|archive-url=https://web.archive.org/web/20141225213456/http://samag.ru/archive/article/2759}}</ref> the use of PSAP does not require a medical prescription. Such devices are used by hunters, naturalists (for audio observation of animals or birds), ordinary people (for example, to increase the volume of the TV in a quiet room), etc. PSAP models differ significantly in price and functionality. Some devices simply amplify sound. Others contain directional microphones, equalizers to adjust the audio signal gain and filter noise. In modern days, some people refer to these devices as OTC hearing aids.<ref>Beck, Melinda, {{Webarchive|url=https://web.archive.org/web/20170916054140/https://www.wsj.com/articles/SB120156046709123567 |date=16 September 2017 }}, ''The Wall Street Journal,'' 29 January 2008. Retrieved 23 May 2013.</ref>

== Evolution of hearing aid applications ==
There are audio players designed specifically for the hard-of-hearing. These applications amplify the volume of the reproduced audio signal in accordance with the user's hearing characteristics and act as a music volume amplifier and assistive hearing aid. The amplification algorithm works on the frequencies that the user hears worse, thus restoring natural hearing perception of the sound of music.

Just as in hearing aid applications, the player adjustment is based on the user's audiogram.

There are also applications that not only adapt the sound of music but also include some hearing aid functions. Such applications include a sound amplification mode in accordance with the user's hearing characteristics as well as a noise suppression mode and a mode allowing the user to hear ambient sound without pausing the music.

Also, some applications allow the hard-of-hearing to watch video and listen to the radio with comfort. The operational principles of these applications are similar to those of hearing aid applications: the audio signal is amplified on the frequencies that the user hears worse.

== Hearing aid adaptation ==
A person using a hearing aid for the first time often cannot make use of all its advantages quickly.<ref name=":1">{{Cite web|title=Адаптация к слуховому аппарату|url=https://r-sluh.ru/help/rekomendacii/adaptaciya_k_sluhovomu_apparatu/|url-status=live|access-date=28 May 2019|website=r-sluh.ru|language=ru|archive-date=28 May 2019|archive-url=https://web.archive.org/web/20190528010548/https://r-sluh.ru/help/rekomendacii/adaptaciya_k_sluhovomu_apparatu/}}</ref> The structure and characteristics of hearing aids are thoroughly devised by specialists in order to make the adjustment period as simple and quick as possible. However, despite this, a beginning hearing aid user certainly needs time to get used to it.<ref name=":22">{{Cite web|title=Адаптация к слуховому аппарату|url=http://www.xn----ttbbfjpems.xn--p1ai/index.php/sovety-polzovatelyu/27-2012-08-09-04-17-21|archive-url=https://web.archive.org/web/20190528010549/http://www.xn----ttbbfjpems.xn--p1ai/index.php/sovety-polzovatelyu/27-2012-08-09-04-17-21|archive-date=28 May 2019|access-date=28 May 2019|website=www.xn----ttbbfjpems.xn—p1ai|language=ru}}</ref>

The process of adjusting to hearing prostheses consists of the following steps:<ref name=":1" />
* Initial adjustment of the device
* Fine adjustments
* Adaptation to the new sound

Due to the plasticity of the central nervous system, inactive hearing centers in the brain's cortex switch over to processing auditory stimuli in another frequency and intensity. The brain starts to perceive sounds amplified by the hearing aid immediately after the initial adjustment; however, it may not process them correctly right away.<ref name=":1" />

Feeling the hearing aid in the ear may seem unusual. It also takes time to adapt to a new way of hearing. The ear has to be gradually adjusted to the new sound. The sound may seem unnatural, metallic, too loud or too quiet. A whistling sound may also appear, which can be unpleasant.<ref name=":22" />

Hearing aids do not provide immediate improvement. The adjustment period can last from several hours to several months.<ref name=":1" />

Patients are offered an initial schedule to wear their hearing aid, ensuring gradual adaptation to it. If the patient wears the hearing aid continually from the beginning, the unfamiliar sound may cause a headache, and as a result, the user may refuse to wear a hearing aid despite the fact that it helps. Audiologists often run a quick preparation course for the patients. As a rule, users have inflated expectations of hearing aids. They expect that hearing aids will help them to hear in the same way as before hearing loss, but it is not the case. Training sessions help hearing aid users to get accustomed to the feeling of new sounds. Users are strongly recommended to regularly visit an audiologist, including for the purposes of additional hearing aid adjustment.<ref name=":24">{{Cite book|url=https://books.google.com/books?id=4b7jkQEACAAJ|title=Введение в аудиологию и слухопротезирование|last=Королева|first=Инна Васильевна|date=2012|publisher=КАРО|isbn=978-5-9925-0737-9|language=ru|access-date=29 May 2020|archive-date=3 August 2020|archive-url=https://web.archive.org/web/20200803011100/https://books.google.com/books?id=4b7jkQEACAAJ|url-status=live}}</ref>

Hearing aid applications, in contrast to traditional hearing aids, allow the implementation of options such as a built-in adaptation course.

The functions of the course may include:
* control of the amount of time spent on learning;
* control over the sequence of exercises;
* daily reminders to do the exercises.

The goal of the course is to help a user adapt to using a hearing aid application.

The adaptation course includes a certain number of stages, starting from listening to a set of low everyday sounds in a quiet environment, getting accustomed to one's own speech and other people's speech, getting accustomed to speech among background noise, etc.<ref>{{Cite web|url=http://petralex.pro/|title=Free apps help better hearing!|website=PETRALEX Hearing Aid|language=en|access-date=28 May 2019|archive-date=15 May 2018|archive-url=https://web.archive.org/web/20180515172904/http://petralex.pro/|url-status=live}}</ref>

==History==
{{main|History of hearing aids}}
] with ear trumpet]]
The first hearing aids were ]s, and were created in the 17th century. Some of the first hearing aids were external hearing aids. External hearing aids directed sounds in front of the ear and blocked all other noises. The apparatus would fit behind or in the ear.

The movement toward modern hearing aids began with the creation of the telephone, and the first electric hearing aid, the "akouphone", was created about 1895 by ]. By the late 20th century, digital hearing aids were commercially available.<ref name=autogenerated4>{{cite journal|doi=10.1109/MAHC.2011.43|title=Hearing Aids and the History of Electronics Miniaturization|journal=IEEE Annals of the History of Computing|volume=33|issue=2|pages=24–45|year=2011|last1=Mills|first1=Mara|s2cid=10946285}}</ref>

The invention of the ], ], digital signal processing chip or ], and the development of computer technology helped transform the hearing aid to its present form.<ref name=autogenerated3>Howard, Alexander (26 November 1998). {{webarchive|url=https://web.archive.org/web/20161228124730/http://www.nytimes.com/1998/11/26/technology/hearing-aids-smaller-and-smarter.html |date=28 December 2016 }} ''New York Times''.</ref>

===History of digital aids===
The history of DHA can be divided into three stages. '''The first stage''' began in the 1960s with the widespread use of digital computers for simulation of audio processing and for the analysis of systems and algorithms.<ref name="va">{{cite web |url=http://www.rehab.research.va.gov/jour/87/24/4/pdf/levitt.pdf |title=LEVITT: Digital Hearing Aids: A Tutorial Review |publisher=rehab.research.va.gov |access-date=18 February 2015 |archive-date=19 March 2015 |archive-url=https://web.archive.org/web/20150319183136/http://www.rehab.research.va.gov/jour/87/24/4/pdf/levitt.pdf |url-status=live }}</ref> The work was conducted with the help of the very large digital computers of that era. These efforts were not actual digital hearing aids because the computers were not fast enough for audio processing in real time and their size prevented them from being described as wearable, but they allowed successful studies of the various hardware circuits and algorithms for digital processing of audio signals. The software package Block of Compiled Diagrams (BLODI) developed by Kelly, Lockbaum and Vysotskiy in 1961<ref name="wikipedia">{{cite book|author1=Kelly LJ Jr |author2=Lochbaum C |author3=Vyssotsky VA |title=A block diagram compiler. Bell System Tech J (40):669–676, 1961 }}</ref> allowed simulation of any sound system that could be characterized in the form of a block diagram. A special phone was created so that a person with a hearing impairment could listen to the digitally processed signals, but not in real time. In 1967, Harry Levitt used BLODI to simulate a hearing aid on a digital computer.

Almost ten years later '''the second stage''' began with the creation of the hybrid hearing aid, in which the analog components of a conventional hearing aid consisting of amplifiers, filters and signal limiting were combined with a separate digital programmable component in a conventional hearing aid case. The audio processing remained analog but it was controlled by the digital programmable component. The digital component could be programmed by connecting the device to an external computer in the laboratory then disconnected to allow the hybrid device to function as a conventional wearable hearing aid.

The hybrid device was effective from a practical point of view because of the low power consumption and compact size. At that time, low-power analog amplifier technology was well developed in contrast to the available semiconductor chips able to process digital audio in real time. The combination of high performance analog components for real time audio processing and a separate low power digital programmable component only for controlling the analog signal led to the creation of several low power digital programmable components able to implement different types of control.

A hybrid hearing aid was developed by Etymotic Design. A little later, Mangold and Lane<ref name="va"/> created a programmable multi-channel hybrid hearing aid. Graupe<ref name="va2">{{cite web |url=http://www.rehab.research.va.gov/jour/87/24/4/pdf/graupe.pdf |vauthors=Graupe D, Grosspietsch JK, Basseas SP |title=A single microphone-based self-adaptive filter of noise from speech and its performance evaluation. J Rehabil Res Dev 24(4), 1987 (this issue |publisher=rehab.research.va.gov |access-date=18 February 2015 |archive-date=24 September 2015 |archive-url=https://web.archive.org/web/20150924085813/http://www.rehab.research.va.gov/jour/87/24/4/pdf/graupe.pdf |url-status=live }}</ref> with co-authors developed a digital programmable component that implemented an adaptive noise filter.

'''The third stage''' began in the early 1980s by a research group at Central Institute for the Deaf headed up by faculty members at Washington University in St. Louis MO. This group created the first fully digital wearable hearing aid.<ref>Engebretson, AM, Popelka, GR, Morley, RE, Niemoeller, AF, and Heidbreder, AF: A digital hearing aid and computer-based fitting procedure. Hearing Instruments 1986; 37(2): 8-14</ref><ref>Popelka, GR: Computer assisted hearing aid fitting, in Microcomputer Applications in Rehabilitation of Communication Disorders, M.L. Grossfeld and C.A. Grossfeld, Editors. 1986, Aspen Publishing: Rockville, Maryland. 67-95</ref> They first conceived a complete, comprehensive full digital hearing aid, then designed and fabricated, miniaturized full digital computer chips using custom digital signal processing chips with low power and very large scale integrated (VLSI) chip technology able to process both the audio signal in real time and the control signals, yet able to be powered by a battery and be fully wearable as a full digital wearable hearing aid able to be actually used by individuals with hearing loss in real-world environments. Engebretson, Morley and Popelka were the inventors of the first full digital hearing aid. Their work resulted in ] 4,548,082, "Hearing aids, signal supplying apparatus, systems for compensating hearing deficiencies, and methods" by A Maynard Engebretson, Robert E Morley Jr. and Gerald R Popelka, filed in 1984 and issued in 1985. This full digital wearable hearing aid also included many additional features now used in all contemporary full digital hearing aids including a bidirectional interface with an external computer, self-calibration, self-adjustment, wide bandwidth, digital programmability, a fitting algorithm based on audibility, internal storage of digital programs, and fully digital multichannel amplitude compression and output limiting. This group created several of these full digital hearing aids and used them for research on hearing impaired people as they wore them in the same manner as conventional hearing aids in real-world situations. In this first full DHA all stages of sound processing and control were carried out in binary form. The external sound was picked up by a microphone positioned in an ITE ear module to take advantage of the acoustic effects of the pinna, then converted into binary code, digitally processed and digitally controlled in real time, then converted back to an analog signal sent to two miniature loudspeakers positioned in the same ITE ear module. The ITE module also contained an inward facing microphone to measure the sound actually generated in the ear canal, a precursor to separate probe tube measures now routinely used for hearing aid fitting. The necessary electronic components, including batteries, to support this arrangement were situated in a BTE module that could be supplemented with a body worn module. These specialized hearing aid chips continued to become smaller, increase in computational ability and require even less power. Now, virtually all commercial hearing aids are fully digital and their digital signal processing capability has significantly increased. Very small and very low power specialized digital hearing aid chips are now used in all hearing aids manufactured worldwide. Many additional new features also have been added with various on-board advanced wireless technology.<ref>Popelka, GR., Moore, BJC, Popper, AN, and Fay, RR: 2016, Hearing Aids, Springer Science, LLC, NY, NY</ref>

==Regulation==

=== Canada ===
Hearing aids are Class II<ref>{{Cite web |last=Canada |first=Health |date=29 July 2016 |title=Medical batteries |url=https://www.canada.ca/en/health-canada/services/drugs-health-products/medical-devices/activities/announcements/medical-batteries.html |access-date=21 March 2023 |website=www.canada.ca |archive-date=21 March 2023 |archive-url=https://web.archive.org/web/20230321165445/https://www.canada.ca/en/health-canada/services/drugs-health-products/medical-devices/activities/announcements/medical-batteries.html |url-status=live }}</ref> regulated medical devices under ].

Under ], the regulates the safety, quality, and effectiveness of hearing aids. All hearing aids imported and sold in Canada are subject to a pre-market review. Post-market, Health Canada monitors the performance of the hearing aid and any consumer complaints.

Hearing aid financial assistance is available at both the federal and provincial level. Provincial hearing aid assistance and coverage can vary widely depending on the province and territory.<ref>{{Cite web |title=Hearing aid financial assistance in Canada |url=https://www.hearingdirectory.ca/help/hearing-aids/insurance-financial-assistance |access-date=21 March 2023 |website=Hearing Directory |language=en-CA |archive-date=21 March 2023 |archive-url=https://web.archive.org/web/20230321165444/https://www.hearingdirectory.ca/help/hearing-aids/insurance-financial-assistance |url-status=live }}</ref>

In Canada, a prescription is required to purchase hearing aids. Only licensed audiologists, Ear, Nose and Throat (ENT) doctors, hearing instrument practitioners (where the profession exists), and ''audioprothésistes'' (in Quebec)<ref group=note>Although audioprothésistes are allowed to administer hearing tests, to prevents conflicts of interest, the healthcare system will no compensate hearing aids if the test was not performed by an audiologist.</ref> can prescribe hearing aids. Over-the-counter (OTC) hearing aids are currently not available for sale in Canada.

Canadian taxpayers can claim tax relief for hearing aids as a medical expense.<ref>{{Cite web |last=Agency |first=Canada Revenue |date=4 January 2016 |title=Details of medical expenses |url=https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/lines-33099-33199-eligible-medical-expenses-you-claim-on-your-tax-return/details-medical-expenses.html |access-date=21 March 2023 |website=www.canada.ca |archive-date=21 March 2023 |archive-url=https://web.archive.org/web/20230321165445/https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/lines-33099-33199-eligible-medical-expenses-you-claim-on-your-tax-return/details-medical-expenses.html |url-status=live }}</ref>

===Ireland===
Like much of the Irish health care system, hearing aid provision is a mixture of public and private.

Hearing aids are provided by the state to children, OAPs{{Definition needed|date=December 2021}} and to people whose income is at or below that of the state pension. The Irish state hearing aid provision is extremely poor;{{Editorializing|date=December 2021}} people often have to wait for two years for an appointment.{{Citation needed|date=December 2021}}

It is estimated that the total cost to the state of supplying one hearing aid exceeds €2,000.{{Citation needed|date=October 2010}}

Hearing aids are also available privately, and there is grant assistance available for insured workers. For the fiscal year ending 2016, the grant stands at a maximum of €500 per ear.<ref>{{cite web|url=http://www.welfare.ie/EN/Schemes/DentalOpticalAndHearingBenefits/Pages/Aural.aspx|title=Aural|publisher=Ireland Department of Social Protection|access-date=23 July 2012|archive-url=https://web.archive.org/web/20120702195438/http://www.welfare.ie/EN/Schemes/DentalOpticalAndHearingBenefits/Pages/Aural.aspx|archive-date=2 July 2012}}</ref>

Irish taxpayers can also claim tax relief at the standard rate as hearing aids are recognised as a medical device.

Hearing aids in the Republic of Ireland are exempt from VAT.

Hearing aid providers in Ireland mostly belong to the Irish Society of Hearing Aid Audiologists.

===United States===
Ordinary hearing aids are ] regulated medical devices under Federal ] (FDA) rules.<ref name=21USC360k_a>{{USC|21|360k}} (a) (2005).</ref> A 1976 statute explicitly prohibits any state requirement that is "different from, or in addition to, any requirement applicable" to regulated medical devices (which includes hearing aids) which relates "to the safety and effectiveness of the device".<ref name=21USC360k_a/> Inconsistent state regulation is preempted under the federal law.<ref>Missouri Board of Examiners for Hearing Instrument Specialists v. Hearing Help Express, Inc., 447 3d 1033 (8th Cir. 2006)</ref> In the late 1970s, the FDA established federal rules governing hearing aid sales,<ref>Final Rule issued in Docket 76N-0019, {{Federal Register|42|9286}} (15 February 1977).</ref> and addressed various requests by state authorities for exemptions from federal preemption, granting some and denying others.<ref>
Exemption from Preemption of State and Local Hearing Aid Requirements; Applications for Exemption, Docket No. 77N-0333, {{Federal Register|45|67326}}; Medical Devices: Applications for Exemption from Federal Preemption of State and Local hearing Aid Requirements, Docket No. 78P-0222, {{Federal Register|45|67325}} (10 October 1980).</ref> The ] (OTC Act) was passed under the FDA Reauthorization Act of 2017, creating a class of hearing aids regulated by the FDA available directly to consumers without involvement from a licensed professional. This law's provisions are expected to go into effect in 2020.<ref>{{Cite web|url=https://www.congress.gov/bill/115th-congress/house-bill/2430|title=H.R.2430 - 115th Congress (2017-2018): FDA Reauthorization Act of 2017|date=18 August 2017|website=www.congress.gov|access-date=16 March 2020|archive-date=22 February 2020|archive-url=https://web.archive.org/web/20200222024040/https://www.congress.gov/bill/115th-congress/house-bill/2430|url-status=live}}</ref>

In August 2022, the FDA issued a final rule to improve access to hearing aids.<ref name="FDA PR 08162022" /><ref>{{cite web | title=Public Inspection: Medical Devices: Ear, Nose, and Throat Devices; Establishing Over-the-Counter Hearing Aids | publisher=U.S. ] (FDA) | website=Federal Register | date=16 August 2022 | url=https://www.federalregister.gov/public-inspection/2022-17230/medical-devices-ear-nose-and-throat-devices-establishing-over-the-counter-hearing-aids | access-date=16 August 2022 | archive-date=16 August 2022 | archive-url=https://web.archive.org/web/20220816125549/https://www.federalregister.gov/public-inspection/2022-17230/medical-devices-ear-nose-and-throat-devices-establishing-over-the-counter-hearing-aids | url-status=live }} {{PD-notice}}</ref> The action establishes a new category of over-the-counter (OTC) hearing aids, enabling consumers with perceived mild to moderate hearing impairment to purchase hearing aids directly from stores or online retailers without the need for a medical exam, prescription or a fitting adjustment by an audiologist.<ref name="FDA PR 08162022">{{cite web | title=FDA Finalizes Historic Rule Enabling Access to Over-the-Counter Hearing Aids for Millions of Americans | publisher=U.S. ] (FDA) | date=16 August 2022 | url=https://www.fda.gov/news-events/press-announcements/fda-finalizes-historic-rule-enabling-access-over-counter-hearing-aids-millions-americans | access-date=16 August 2022 | archive-date=16 August 2022 | archive-url=https://web.archive.org/web/20220816133009/https://www.fda.gov/news-events/press-announcements/fda-finalizes-historic-rule-enabling-access-over-counter-hearing-aids-millions-americans | url-status=live }} {{PD-notice}}</ref> The FDA action amends existing rules that apply to prescription hearing aids for consistency with the new OTC category, it repeals the conditions for sale for hearing aids, and it includes provisions that address some of the effects of the FDA OTC hearing aid regulations on state regulation of hearing aids.<ref name="FDA PR 08162022" /> The FDA also issued the final guidance, Regulatory Requirements for Hearing Aid Devices and Personal Sound Amplification Products (PSAPs), to clarify the differences between hearing aids, which are medical devices, and PSAPs, consumer products that help people with normal hearing amplify sounds.<ref name="FDA PR 08162022" /><ref>{{cite web | title=Regulatory Requirements for Hearing Aids and PSAPs Guidance | publisher=U.S. ] (FDA) | date=12 August 2022 | url=https://www.fda.gov/regulatory-information/search-fda-guidance-documents/regulatory-requirements-hearing-aid-devices-and-personal-sound-amplification-products | access-date=16 August 2022 | archive-date=16 August 2022 | archive-url=https://web.archive.org/web/20220816133009/https://www.fda.gov/regulatory-information/search-fda-guidance-documents/regulatory-requirements-hearing-aid-devices-and-personal-sound-amplification-products | url-status=live }} {{PD-notice}}</ref>

==Cost==
], Ireland]]

Several industrialized countries supply free or heavily discounted hearing aids through their ] system.

===Australia===
The Australian ] provides eligible Australian citizens and residents with a basic hearing aid free-of-charge, though recipients can pay a "top up" charge if they wish to upgrade to a hearing aid with more or better features. Maintenance of these hearing aids and a regular supply of batteries is also provided, on payment of a small annual maintenance fee.<ref>{{cite web|url=http://www6.health.gov.au/internet/wcms/publishing.nsf/Content/health-hear-understanding |title=Understanding the Australian Government Hearing Services Program |access-date=4 December 2007 |archive-url=https://web.archive.org/web/20070909102734/http://www.health.gov.au/internet/wcms/publishing.nsf/Content/health-hear-understanding |archive-date=9 September 2007 }}</ref>

===Canada===
In Canada, health care is a responsibility of the ]. In the province of ], the price of hearing aids is partially reimbursed through the Assistive Devices Program of the ], up to $500 for each hearing aid. Like eye appointments, audiological appointments are no longer covered through the provincial public health plan. Audiometric testing can still easily be obtained, often free of charge, in private sector hearing aid clinics and some ear, nose and throat doctors offices. Hearing aids may be covered to some extent by private insurance or in some cases through government programs such as ] or ].

===Iceland===
Social Insurance pays a one time fee of ISK 30,000 for any kind of hearing aid. However, the rules are complicated{{Editorializing|date=December 2021}} and require that both ears have significant hearing loss in order to qualify for reimbursement. BTE hearing aids range from ISK 60,000 to ISK 300,000.<ref> Accessed 30 November 2007 {{webarchive |url=https://web.archive.org/web/20080216165527/http://www.tr.is/english |date=16 February 2008 }}</ref>

===India===
In India hearing aids of all kinds are easily available. Under central and state government health services, the poor can often avail themselves of free hearing devices. However, market prices vary for others and can range from Rs 10,000 to Rs 275,000 per ear.

===United Kingdom===
From 2000 to 2005 the Department of Health worked with ] (then called RNID) to improve the quality of NHS hearing aids so every NHS audiology department in England was fitting digital hearing aids by March 2005. By 2003 over 175,000 NHS digital hearing aids had been fitted to 125,000 people. Private companies were recruited to enhance the capacity, and two were appointed – David Ormerod Hearing Centres, partly owned by ] and Ultravox Group, a subsidiary of ].<ref>{{cite news|title=Loud and clear|url=http://www.hsj.co.uk/news/loud-and-clear/20994.article|access-date=17 October 2014|publisher=Health Service Journal|date=18 December 2003|url-status=live|archive-url=https://web.archive.org/web/20141023061743/http://www.hsj.co.uk/news/loud-and-clear/20994.article|archive-date=23 October 2014}}</ref>

Within the UK, the ] provides digital BTE hearing aids to NHS patients, on long-term loan, free of charge. Other than BAHAs (]) or cochlear implants, where specifically required, BTEs are usually the only style available. Private purchases may be necessary if a user desires a different style. Batteries are free.<ref> Accessed 26 November 2007 {{webarchive |url=https://web.archive.org/web/20101002061033/http://www.rnid.org.uk/VirtualContent/101701/NHS_hearing_aid_service_September_2009.pdf |date=2 October 2010 }}</ref>

In 2014 the ] in North Staffordshire considered proposals to end provision of free hearing aids for adults with mild to moderate age related hearing loss, which currently cost them £1.2m a year. Action on Hearing Loss mobilised a campaign against the proposal.<ref>{{cite news|title=Hearing aid charging opposed in feedback exercise|url=http://www.hsj.co.uk/hsj-local/ccgs/nhs-north-staffordshire-ccg/hearing-aid-charging-opposed-in-feedback-exercise/5074952.article|access-date=17 October 2014|publisher=Health Service Journal|date=23 September 2014|url-status=live|archive-url=https://web.archive.org/web/20141009012011/http://www.hsj.co.uk/hsj-local/ccgs/nhs-north-staffordshire-ccg/hearing-aid-charging-opposed-in-feedback-exercise/5074952.article|archive-date=9 October 2014}}</ref>

In June 2018 the ] produced new guidance saying that hearing aids should be offered at the first opportunity when hearing loss affects the individual's ability to hear and communicate, rather than waiting for arbitrary thresholds of hearing loss to be reached.<ref name="b832">{{cite web | title=Hearing loss in adults: assessment and management | publisher=NICE | date=2018-06-21 | url=https://www.nice.org.uk/guidance/ng98 | access-date=2024-07-05}}</ref>

===United States===
Most private ] in the United States do not provide coverage for hearing aids, so all costs are usually borne by the recipient. The cost for a single hearing aid can vary between $500 and $6,000 or more, depending on the level of technology and whether the clinician bundles fitting fees into the cost of the hearing aid. Though if an adult has ] which substantially limits major life activities, some state-run vocational rehabilitation programs can provide upwards of full financial assistance. Severe and profound hearing loss often falls within the "substantially limiting" category.<ref>{{cite web |url=http://www.eeoc.gov/facts/deafness.html |website=U.S. Equal Employment Opportunity Commission |title=Questions and Answers about Deafness and Hearing Impairments in the Workplace and the Americans with Disabilities Act |archive-url=https://web.archive.org/web/20160304034623/http://www.eeoc.gov/facts/deafness.html |archive-date=4 March 2016 |access-date=26 November 2007 }}</ref> Less expensive hearing aids can be found on the internet or mail order catalogs, but most in the under-$200 range tend to amplify the low frequencies of background noise, making it harder to hear the human voice.<ref>{{cite news |url=https://www.chicagotribune.com/2011/03/09/now-hear-this-12/ |first=Barbara |last=Mahany |title=Now Hear This |archive-url=https://web.archive.org/web/20130615015524/http://articles.chicagotribune.com/2011-03-09/health/sc-health-0309-hearing-aid-20110309_1_hearing-aid-hearing-loss-hearing-loss-association |archive-date=15 June 2013 |newspaper=Chicago Tribune |url-status=live |date=9 March 2011 }}</ref><ref>{{cite web |last=Romano |first=Tricia |date=22 October 2012 |url=http://well.blogs.nytimes.com/2012/10/22/the-hunt-for-an-affordable-hearing-aid/ |title=The Hunt for an Affordable Hearing Aid |archive-url=https://web.archive.org/web/20150225230300/http://well.blogs.nytimes.com/2012/10/22/the-hunt-for-an-affordable-hearing-aid/ |archive-date=25 February 2015 |url-status=live |website=Well |publisher=New York Times }}</ref>

Military veterans receiving VA medical care are eligible for hearing aids based on medical need. The Veterans Administration pays the full cost of testing and hearing aids to qualified military veterans. Major VA medical facilities provide complete diagnostic and audiology services.{{citation needed|date=January 2018}}

The cost of hearing aids is a ] medical expense for those who ] medical deductions.<ref>{{cite web |url=https://www.irs.gov/taxtopics/tc502.html |website=Internal Revenue Service |title=Topic 502 – Medical and Dental Expenses |archive-url=https://web.archive.org/web/20170703035600/https://www.irs.gov/taxtopics/tc502.html |archive-date=3 July 2017 |url-status=live |access-date=26 November 2007 }}</ref>

Research involving more than 40,000 US households showed a convincing correlation between the degree of hearing loss and the reduction of personal income. According to the same research, hearing aids were shown to mitigate the impact of income loss by 90%–100% for those with milder hearing losses and from 65%–77% for those with severe to moderate hearing loss.<ref name="lww2">{{cite journal |first=Sergei |last=Kochkin |title=MarkeTrak VIII: The efficacy of hearing aids in achieving compensation equity in the workplace |journal=The Hearing Journal |date=October 2010 |volume=63 |number=10 |pages=19–24, 26, 28 |doi=10.1097/01.HJ.0000389923.80044.e6 |s2cid=52230904 |doi-access=free }}</ref>

==Batteries==
While there are some instances that a hearing aid uses a rechargeable battery or a long-life disposable battery, the majority of modern hearing aids use one of five standard ] ]. (Older hearing aids often used ] cells, but these cells have become banned in most countries today.) Modern hearing aid button cell types are typically referred to by their common number name or the color of their packaging.

They are typically loaded into the hearing aid via a rotating battery door, with the flat side (case) as the positive terminal (]) and the rounded side as the negative terminal (]).

These batteries all operate from 1.35 to 1.45 ]s.

The type of battery a specific hearing aid utilizes depends on the physical size allowable and the desired lifetime of the battery, which is in turn determined by the ] draw of the hearing aid device. Typical battery lifetimes run between 1 and 14 days (assuming 16-hour days).

{| class=wikitable style="text-align: center; width:100%"
|+'''Hearing Aid Battery Types'''
|-
! style="width:10%;"|Type/ Color Code
! style="width:15%;"|Dimensions (Diameter×Height)
! style="width:15%;"|Common Uses
! style="width:10%;"|Standard Names
! style="width:50%;"|Misc Names
|-
| style="background:blue; color:white;"|'''675'''||11.6&nbsp;mm × 5.4&nbsp;mm||High-Power ]s, ]||]: PR44, ]: 7003ZD||675, 675A, 675AE, 675AP, 675CA, 675CP, 675HP, 675HPX, 675 Implant Plus, 675P (HP), 675PA, 675SA, 675SP, A675, A675P, AC675, AC675E, AC675E/EZ, AC675EZ, AC-675E, AP675, B675PA, B6754, B900PA, C675, DA675, DA675H, DA675H/N, DA675N, DA675X, H675AE, L675ZA, ME9Z, P675, P675i+, PR44, PR44P, PR675, PR675H, PR675P, PR-675PA, PZ675, PZA675, R675ZA, S675A, V675, V675A, V675AT, VT675, XL675, Z675PX, ZA675, ZA675HP
|-
| style="background:orange; color:black;"|'''13'''||7.9&nbsp;mm × 5.4&nbsp;mm||]s, ]s||]: PR48, ]: 7000ZD||13, 13A, 13AE, 13AP, 13HP, 13HPX, 13P, 13PA, 13SA, 13ZA, A13, AC13, AC13E, AC13E/EZ, AC13EZ, AC-13E, AP13, B13BA, B0134, B26PA, CP48, DA13, DA13H, DA13H/N, DA13N, DA13X, E13E, L13ZA, ME8Z, P13, PR13, PR13H, PR-13PA, PZ13, PZA13, R13ZA, S13A, V13A, VT13, V13AT, W13ZA, XL13, ZA13
|-
| style="background:brown; color:white;"|'''312'''||7.9&nbsp;mm × 3.6&nbsp;mm||mini]s, ]s, ]s||]: PR41, ]: 7002ZD||312, 312A, 312AE, 312AP, 312HP, 312HPX, 312P, 312PA, 312SA, 312ZA, AC312, AC312E, AC312E/EZ, AC312EZ, AC-312E, AP312, B312BA, B3124, B347PA, CP41, DA312, DA312H, DA312H/N, DA312N, DA312X, E312E, H312AE, L312ZA, ME7Z, P312, PR312, PR312H, PR-312PA, PZ312, PZA312, R312ZA, S312A, V312A, V312AT, VT312, W312ZA, XL312, ZA312
|-
| style="background:yellow; color:black;"|'''10'''||5.8&nbsp;mm × 3.6&nbsp;mm||]s, ]s||]: PR70, ]: 7005ZD||10, 10A, 10AE, 10AP, 10DS, 10HP, 10HPX, 10SA, 10UP, 20PA, 230, 230E, 230EZ, 230HPX, AC10, AC10EZ, AC10/230, AC10/230E, AC10/230EZ, AC230, AC230E, AC230E/EZ, AC230EZ, AC-230E, AP10, B0104, B20BA, B20PA, CP35, DA10, DA10H, DA10H/N, DA10N, DA230, DA230/10, L10ZA, ME10Z, P10, PR10, PR10H, PR230H, PR536, PR-10PA, PR-230PA, PZA230, R10ZA, S10A, V10, VT10, V10AT, V10HP, V230AT, W10ZA, XL10, ZA10
|-
| style="background:red; color:white;"|'''5'''||5.8&nbsp;mm × 2.1&nbsp;mm||CICs||]: PR63, ]: 7012ZD||5A, 5AE, 5HPX, 5SA, AC5, AC5E, AP5, B7PA, CP63, CP521, L5ZA, ME5Z, P5, PR5H, PR-5PA, PR521, R5ZA, S5A, V5AT, VT5, XL5, ZA5
|}

== See also ==

* ]
* ] (ABR)
* ]
* ]
* ]
* ]
* ]
* ]
* ] (BAHA)
* ]
* ]
* ]
* ]
* ] (ENG/VNG)
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]

== Notes and references ==
{{NoteFoot}}
{{reflist}}


== Further reading ==
* {{cite journal | vauthors = Chen CH, Huang CY, Cheng HL, Lin HH, Chu YC, Chang CY, Lai YH, Wang MC, Cheng YF | display-authors = 6 | title = Comparison of personal sound amplification products and conventional hearing aids for patients with hearing loss: A systematic review with meta-analysis | journal = eClinicalMedicine | volume = 46 | page = 101378 | date = April 2022 | pmid = 35434580 | pmc = 9006672 | doi = 10.1016/j.eclinm.2022.101378 }}
* {{cite journal | vauthors = Mamo SK, Reed NS, Nieman CL, Oh ES, Lin FR | title = Personal Sound Amplifiers for Adults with Hearing Loss | journal = The American Journal of Medicine | volume = 129 | issue = 3 | pages = 245–50 | date = March 2016 | pmid = 26498713 | pmc = 4755807 | doi = 10.1016/j.amjmed.2015.09.014 }}


==External links== ==External links==
{{commons category|Hearing aids}}
* Hearing aid and hearing loss information site.
* Brief information on hearing aids * ] (NIH)
* U.S. ] (FDA)
* Find an Audiologist, and get more information on hearing loss.
* , World Health Organization.
*.
*
*

*.
{{Portal bar|Medicine|Technology}}
*
{{Authority control}}
]
]


{{DEFAULTSORT:Hearing Aid}}
]
]
]
] ]
] ]
]
]
]
]
]

Latest revision as of 12:44, 13 December 2024

Electroacoustic device

Medical intervention
Hearing aid
In-the-canal hearing aid
Other namesDeaf aid
[edit on Wikidata]

A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers such as personal sound amplification products (PSAPs) or other plain sound reinforcing systems cannot be sold as "hearing aids".

Early devices, such as ear trumpets or ear horns, were passive amplification cones designed to gather sound energy and direct it into the ear canal.

Modern devices are computerised electroacoustic systems that transform environmental sound to make it audible, according to audiometrical and cognitive rules. Modern devices also utilize sophisticated digital signal processing, aiming to improve speech intelligibility and comfort for the user. Such signal processing includes feedback management, wide dynamic range compression, directionality, frequency lowering, and noise reduction.

Modern hearing aids require configuration to match the hearing loss, physical features, and lifestyle of the wearer. The hearing aid is fitted to the most recent audiogram and is programmed by frequency. This process called "fitting" can be performed by the user in simple cases, by a Doctor of Audiology, also called an audiologist (AuD), or by a Hearing Instrument Specialist (HIS) or audioprosthologist. The amount of benefit a hearing aid delivers depends in large part on the quality of its fitting. Almost all hearing aids in use in the US are digital hearing aids, as analog aids are phased out. Devices similar to hearing aids include the osseointegrated auditory prosthesis (formerly called the bone-anchored hearing aid) and cochlear implant.

Uses

Hearing aids are used for a variety of pathologies including sensorineural hearing loss, conductive hearing loss, and single-sided deafness. Hearing aid candidacy was traditionally determined by a Doctor of Audiology, or a certified hearing specialist, who will also fit the device based on the nature and degree of the hearing loss being treated. The amount of benefit experienced by the user of the hearing aid is multi-factorial, depending on the type, severity, and etiology of the hearing loss, the technology and fitting of the device, and on the motivation, personality, lifestyle, and overall health of the user. Over-the-counter hearing aids, which address mild to moderate hearing loss, are designed to be adjusted by the user.

Hearing aids are incapable of truly correcting a hearing loss; they are an aid to make sounds more audible. The most common form of hearing loss for which hearing aids are sought is sensorineural, resulting from damage to the hair cells and synapses of the cochlea and auditory nerve. Sensorineural hearing loss reduces the sensitivity to sound, which a hearing aid can partially accommodate by making sound louder. Other decrements in auditory perception caused by sensorineural hearing loss, such as abnormal spectral and temporal processing, and which may negatively affect speech perception, are more difficult to compensate for using digital signal processing and in some cases may be exacerbated by the use of amplification. Conductive hearing losses, which do not involve damage to the cochlea, tend to be better treated by hearing aids; the hearing aid is able to sufficiently amplify sound to account for the attenuation caused by the conductive component. Once the sound is able to reach the cochlea at normal or near-normal levels, the cochlea and auditory nerve are able to transmit signals to the brain normally.

Common issues with hearing aid fitting and use are the occlusion effect, loudness recruitment, and understanding speech in noise. Once a common problem, feedback is generally now well-controlled through the use of feedback management algorithms.

Candidacy and acquisition

There are several ways of evaluating how well a hearing aid compensates for hearing loss. One approach is audiometry which measures a subject's hearing levels in laboratory conditions. The threshold of audibility for various sounds and intensities is measured in a variety of conditions. Although audiometric tests may attempt to mimic real-world conditions, the patient's own every day experiences may differ. An alternative approach is self-report assessment, where the patient reports their experience with the hearing aid.

Hearing aid outcome can be represented by three dimensions:

  1. hearing aid usage
  2. aided speech recognition
  3. benefit/satisfaction

The most reliable method for assessing the correct adjustment of a hearing aid is through real ear measurement. Real ear measurements (or probe microphone measurements) are an assessment of the characteristics of hearing aid amplification near the ear drum using a silicone probe tube microphone.

Current research is also pointing towards hearing aids and proper amplification as a treatment for tinnitus, a medical condition which manifests itself as a ringing or buzzing in the ears.

Types

There are many types of hearing aids (also known as hearing instruments), which vary in size, power and circuitry. Among the different sizes and models are:

  • Vacuum tube hearing aid, circa 1944 Vacuum tube hearing aid, circa 1944
  • Transistor body-worn hearing aid. Transistor body-worn hearing aid.
  • Pair of BTE hearing aids with earmolds. Pair of BTE hearing aids with earmolds.
  • Receiver-in-the-canal hearing aids Receiver-in-the-canal hearing aids
  • In-the-ear hearing aid In-the-ear hearing aid
  • In-the-canal hearing aid In-the-canal hearing aid
  • Woman wearing a bone anchored hearing aid Woman wearing a bone anchored hearing aid
  • Hearing aid application Hearing aid application

Body-worn

Body worn aids were the first portable electronic hearing aids, and were invented by Harvey Fletcher while working at Bell Laboratories. Body aids consist of a case and an earmold, attached by a wire. The case contains the electronic amplifier components, controls and battery, while the earmold typically contains a miniature loudspeaker. The case is typically about the size of a pack of playing cards and is carried in a pocket or on a belt. Without the size constraints of smaller hearing devices, body worn aid designs can provide large amplification and long battery life at a lower cost. Body aids are still used in emerging markets because of their relatively low cost.

Behind the ear

A modern behind the ear hearing aid. The audio tube to the speaker is barely visible.
A modern behind the ear hearing aid with a minicell battery

Behind the ear hearing aids are one of two major classes of hearing aids – behind the ear (BTE) and in the ear (ITE). These two classes are distinguished by where the hearing aid is worn. BTE hearing aids consist of a case which hangs behind the pinna. The case is attached to an earmold or dome tip by a traditional tube, slim tube, or wire. The tube or wire courses from the superior-ventral portion of the pinna to the concha, where the ear mold or dome tip inserts into the external auditory canal. The case contains the electronics, controls, battery, and microphone(s).The loudspeaker, or receiver, may be housed in the case (traditional BTE) or in the earmold or dome tip (receiver-in-the-canal, or RIC). The RIC style of BTE hearing aid is often smaller than a traditional BTE and more commonly used in more active populations.

BTEs are generally capable of providing more output and may therefore be indicated for more severe degrees of hearing loss. However, BTEs are very versatile and can be used for nearly any kind of hearing loss. BTEs come in a variety of sizes, ranging from a small, "mini BTE", to larger, ultra-power devices. Size typically depends on the output level needed, the location of the receiver, and the presence or absence of a telecoil. BTEs are durable, easy to repair, and often have controls and battery doors that are easier to manipulate. BTEs are also easily connected to assistive listening devices, such as FM systems and induction loops. BTEs are commonly worn by children who need a durable type of hearing aid.

In the ear

In the ear aids (ITE) devices fit in the outer ear bowl (called the concha). Being larger, these are easier to insert and can hold extra features. They are sometimes visible when standing face to face with someone. ITE hearing aids are custom made to fit each individual's ear. They can be used in mild to some severe hearing losses. Feedback, a squealing/whistling caused by sound (particularly high frequency sound) leaking and being amplified again, may be a problem for severe hearing losses. Some modern circuits are able to provide feedback regulation or cancellation to assist with this. Venting may also cause feedback. A vent is a tube primarily placed to offer pressure equalization. However, different vent styles and sizes can be used to influence and prevent feedback. Traditionally, ITEs have not been recommended for young children because their fit could not be as easily modified as the earmold for a BTE, and thus the aid had to be replaced frequently as the child grew. However, there are new ITEs made from a silicone type material that mitigates the need for costly replacements. ITE hearing aids can be connected wirelessly to FM systems, for instance with a body-worn FM receiver with induction neck-loop which transmits the audio signal from the FM transmitter inductively to the telecoil inside the hearing instrument.

Mini in canal (MIC) or completely in canal (CIC) aids are generally not visible unless the viewer looks directly into the wearer's ear. These aids are intended for mild to moderately severe losses. CICs are usually not recommended for people with good low-frequency hearing, as the occlusion effect is much more noticeable. Completely-in-the-canal hearing aids fit tightly deep in the ear. It is barely visible. Being small, it will not have a directional microphone, and its small batteries will have a short life, and the batteries and controls may be difficult to manage. Its position in the ear prevents wind noise and makes it easier to use phones without feedback. In-the-canal hearing aids are placed deep in the ear canal. They are barely visible. Larger versions of these can have directional microphones. Being in the canal, they are less likely to cause a plugged feeling. These models are easier to manipulate than the smaller completely in-the-canal models but still have the drawbacks of being rather small.

In-the-ear hearing aids are typically more expensive than behind-the-ear counterparts of equal functionality, because they are custom fitted to the patient's ear. In fitting, the audiologist takes a physical impression (mold) of the ear. The mold is scanned by a specialized CAD system, resulting in a 3D model of the outer ear. During modeling, the venting tube is inserted. The digitally modeled shell is printed using a rapid prototyping technique such as stereolithography. Finally, the aid is assembled and shipped to the audiologist after a quality check.

Invisible-in-canal hearing aids

Invisible-in-canal hearing aids (IIC) style of hearing aids fits inside the ear canal completely, leaving little to no trace of an installed hearing aid visible. This is because it fits deeper in the canal than other types, so that it is out of view even when looking directly into the ear bowl (concha). A comfortable fit is achieved because the shell of the aid is custom-made to the individual ear canal after taking a mold. Invisible hearing aid types use venting and their deep placement in the ear canal to give a more natural experience of hearing. Unlike other hearing aid types, with the IIC aid the majority of the ear is not blocked (occluded) by a large plastic shell. This means that sound can be collected more naturally by the shape of the ear, and can travel down into the ear canal as it would with unassisted hearing. Depending on their size, some models allow the wearer to use a mobile phone as a remote control to alter memory and volume settings, instead of taking the IIC out to do this. IIC types are most suitable for users up to middle age, but are not suitable for elderly people with unsteady hands.

Extended wear hearing aids

Main article: Extended wear hearing aid

Extended wear hearing aids are hearing devices that are non-surgically placed in the ear canal by a hearing professional. The extended wear hearing aid represents the first "invisible" hearing device. These devices are worn for 1–3 months at a time without removal. They are made of soft material designed to contour to each user and can be used by people with mild to moderately severe hearing loss. Their close proximity to the ear drum results in improved sound directionality and localization, reduced feedback, and improved high frequency gain. While traditional BTE or ITC hearing aids require daily insertion and removal, extended wear hearing aids are worn continuously and then replaced with a new device. Users can change volume and settings without the aid of a hearing professional. The devices are very useful for active individuals because their design protects against moisture and earwax and can be worn while exercising, showering, etc. Because the device's placement within the ear canal makes them invisible to observers, extended wear hearing aids are popular with those who are self-conscious about the aesthetics of BTE or ITC hearing aid models. As with other hearing devices, compatibility is based on an individual's hearing loss, ear size and shape, medical conditions, and lifestyle. The disadvantages include regular removal and reinsertion of the device when the battery dies, inability to go underwater, earplugs when showering, and for some discomfort with the fit since it is inserted deeply in the ear canal, the only part of the body where skin rests directly on top of bone.

CROS hearing aid

Main article: CROS hearing aid

A CROS hearing aid is a hearing aid that transmits auditory information from one side of the head to the other side of the head. Candidates include people who have poor word understanding on one side, no hearing on one side, or who are not benefiting from a hearing aid on one side. CROS hearing aids can appear very similar to behind the ear hearing aids. The CROS system can assist the patient in sound localization and understanding auditory information on their poor side. While CROS hearing aids can be quite effective, the long-term solution for those with hearing issues on one side is to use a BiCROS system. This creates more of a balance for wearers.

Bone-anchored

Main article: Bone anchored hearing aid

A bone anchored hearing aid (BAHA) is a surgically implanted auditory prosthetic based on bone conduction. It is an option for patients without external ear canals, when conventional hearing aids with a mold in the ear cannot be used. The BAHA uses the skull as a pathway for sound to travel to the inner ear. For people with conductive hearing loss, the BAHA bypasses the external auditory canal and middle ear, stimulating the functioning cochlea. For people with unilateral hearing loss, the BAHA uses the skull to conduct the sound from the deaf side to the side with the functioning cochlea.

Individuals under the age of two (five in the USA) typically wear the BAHA device on a Softband. This can be worn from the age of one month as babies tend to tolerate this arrangement very well. When the child's skull bone is sufficiently thick, a titanium "post" can be surgically embedded into the skull with a small abutment exposed outside the skin. The BAHA sound processor sits on this abutment and transmits sound vibrations to the external abutment of the titanium implant. The implant vibrates the skull and inner ear, which stimulate the nerve fibers of the inner ear, allowing hearing.

The surgical procedure is simple both for the surgeon, involving very few risks for the experienced ear surgeon. For the patient, minimal discomfort and pain is reported. Patients may experience numbness of the area around the implant as small superficial nerves in the skin are sectioned during the procedure. This often disappears after some time. There is no risk of further hearing loss due to the surgery. One important feature of the BAHA is that, if a patient for whatever reason does not want to continue with the arrangement, it takes the surgeon less than a minute to remove it. The BAHA does not restrict the wearer from any activities such as outdoor life, sporting activities etc.

A BAHA can be connected to an FM system by attaching a miniaturized FM receiver to it.

Two main brands manufacture BAHAs today – the original inventors Cochlear, and the hearing aid company Oticon.

Eyeglass aids

1940s adult and child combined hearing aid glasses, on display at Thackray Museum of Medicine.

During the late 1950s through 1970s, before in-the-ear aids became common (and in an era when thick-rimmed eyeglasses were popular), people who wore both glasses and hearing aids frequently chose a type of hearing aid that was built into the temple pieces of the spectacles. However, the combination of glasses and hearing aids was inflexible: the range of frame styles was limited, and the user had to wear both hearing aids and glasses at once or wear neither. Today, people who use both glasses and hearing aids can use in-the-ear types, or rest a BTE neatly alongside the arm of the glasses. There are still some specialized situations where hearing aids built into the frame of eyeglasses can be useful, such as when a person has hearing loss mainly in one ear: sound from a microphone on the "bad" side can be sent through the frame to the side with better hearing.

This can also be achieved by using CROS or bi-CROS style hearing aids, which are now wireless in sending sound to the better side.

Spectacle hearing aids

These are generally worn by people with a hearing loss who either prefer a more cosmetic appeal of their hearing aids by being attached to their glasses or where sound cannot be passed in the normal way, via a hearing aids, perhaps due to a blockage in the ear canal. pathway or if the client experiences continual infections in the ear. Spectacle aids come in two forms, bone conduction spectacles and air conduction spectacles.

Bone conduction spectacles

Sounds are transmitted via a receiver attached from the arm of the spectacles which are fitted firmly behind the boney portion of the skull at the back of the ear, (mastoid process) by means of pressure, applied on the arm of the spectacles. The sound is passed from the receiver on the arm of the spectacles to the inner ear (cochlea), via the bony portion. The process of transmitting the sound through the bone requires a great amount of power. Bone conduction aids generally have a poorer high pitch response and are therefore best used for conductive hearing losses or where it is impractical to fit standard hearing aids.

Air conduction spectacles

Unlike the bone conduction spectacles the sound is transmitted via hearing aids which are attached to the arm or arms of the spectacles. When removing your glasses for cleaning, the hearing aids are detached at the same time. Whilst there are genuine instances where spectacle aids are a preferred choice, they may not always be the most practical option.

Directional spectacles

These 'hearing glasses' incorporate a directional microphone capability: four microphones on each side of the frame effectively work as two directional microphones, which are able to discern between sound coming from the front and sound coming from the sides or back of the user. This improves the signal-to-noise ratio by allowing for amplification of the sound coming from the front, the direction in which the user is looking, and active noise control for sounds coming from the sides or behind. Only very recently has the technology required become small enough to be fitted in the frame of the glasses. As a recent addition to the market, this new hearing aid is currently available only in the Netherlands and Belgium.

Stethoscope

These hearing aids are designed for medical practitioners with hearing loss who use stethoscopes. The hearing aid is built into the speaker of the stethoscope, which amplifies the sound.

Hearing aid applications

Hearing aid applications (HAA) are software which, when installed on mobile computational platforms, transforms them into hearing aids.

The principle of HAA operation corresponds to the basic principles of operation of traditional hearing aids: the microphone receives an acoustic signal and converts it into a digital form. Sound amplification is achieved by the means of a mobile computational platform, in accordance with the degree and type of the user's hearing loss. The processed audio signal is transformed into an audio signal and output to the user into the headphones/headset. Signal processing is implemented in real time.

Constructional features of mobile computational platforms imply preferred use of stereo headsets with two speakers, which allows carrying out binaural hearing correction for the left and right ear separately. HAAs can work with both wired and wireless headsets and headphones.

As a rule, HAAs have two operation modes: setup mode and hearing aid mode. Setup mode involves the user passing an in situ-audiometry procedure, which determines the user's hearing characteristics. Hearing aid mode is a hearing correction system that corrects the user's hearing in accordance with the user's hearing thresholds. HAAs also incorporate background noise suppression and acoustic feedback suppression.

The user can independently choose a formula to enhance the sound, as well as adjust the level of the desired amplification to their wishes.

HAAs have several advantages (compared to traditional hearing aids):

  • HAAs do not cause any psychological inconvenience;
  • it is possible to achieve the highest sound pressure level and get high sound quality (due to large speakers and a long battery life);
  • it is possible to use more complex audio signal processing algorithms and a higher sampling rate (because of capacious battery);
  • the possibility to implement more convenient application control functions for people with poor motor skills;
  • resistance to ingress of earwax and moisture;
  • software flexibility;
  • the large distance between the microphone and the speaker prevents the occurrence of acoustic feedback;
  • the set up of HAAs in simple cases does not require special equipment and qualifications;
  • the user does not need to purchase and carry any separate device;
  • various types of headphones and headsets can be used.

HAAs also have some disadvantages (compared to traditional hearing aids):

  • because the microphone is not located in the ear, it does not use the functional advantages of the auricle and the natural acoustics of the outer ear.
  • they are more noticeable and less comfortable to wear.

Technology

See also: History of hearing aids

The first electrical hearing aid used the carbon microphone of the telephone and was introduced in 1896. The vacuum tube made electronic amplification possible, but early versions of amplified hearing aids were too heavy to carry around. Miniaturization of vacuum tubes lead to portable models, and after World War II, wearable models using miniature tubes. The transistor invented in 1948 was well suited to the hearing aid application due to low power and small size; hearing aids were an early adopter of transistors. The development of integrated circuits allowed further improvement of the capabilities of wearable aids, including implementation of digital signal processing techniques and programmability for the individual user's needs.

Compatibility with telephones

A sign in a train station explains that the public announcement system uses a "Hearing Induction Loop" (audio induction loop). Hearing aid users can use a telecoil (T) switch to hear announcements directly through their hearing aid receiver.

A hearing aid and a telephone are "compatible" when they can connect to each other in a way that produces clear, easily understood sound. The term "compatibility" is applied to all three types of telephones (wired, cordless, and mobile). There are two ways telephones and hearing aids can connect with each other:

  • Acoustically: the sound from the phone's speaker is picked up by the hearing aid's microphone.
  • Electromagnetically: the signal inside the phone's speaker is picked up by the hearing aid's "telecoil" or "T-coil", a special loop of wire inside the hearing aid.

Note that telecoil coupling has nothing to do with the radio signal in a cellular or cordless phone: the audio signal picked up by the telecoil is the weak electromagnetic field that is generated by the voice coil in the phone's speaker as it pushes the speaker cone back and forth.

The electromagnetic (telecoil) mode is usually more effective than the acoustic method. This is mainly because the microphone is often automatically switched off when the hearing aid is operating in telecoil mode, so background noise is not amplified. Since there is an electronic connection to the phone, the sound is clearer and distortion is less likely. But in order for this to work, the phone has to be hearing-aid compatible. More technically, the phone's speaker has to have a voice coil that generates a relatively strong electromagnetic field. Speakers with strong voice coils are more expensive and require more energy than the tiny ones used in many modern telephones; phones with the small low-power speakers cannot couple electromagnetically with the telecoil in the hearing aid, so the hearing aid must then switch to acoustic mode. Also, many mobile phones emit high levels of electromagnetic noise that creates audible static in the hearing aid when the telecoil is used. A workaround that resolves this issue on many mobile phones is to plug a wired (not Bluetooth) headset into the mobile phone; with the headset placed near the hearing aid the phone can be held far enough away to attenuate the static. Another method is to use a "neckloop" (which is like a portable, around-the-neck induction loop), and plug the neckloop directly into the standard audio jack (headphones jack) of a smartphone (or laptop, or stereo, etc.). Then, with the hearing aids' telecoil turned on (usually a button to press), the sound will travel directly from the phone, through the neckloop and into the hearing aids' telecoils.

On 21 March 2007, the Telecommunications Industry Association issued the TIA-1083 standard, which gives manufacturers of cordless telephones the ability to test their products for compatibility with most hearing aids that have a T-Coil magnetic coupling mode. With this testing, digital cordless phone manufacturers will be able to inform consumers about which products will work with their hearing aids.

The American National Standards Institute (ANSI) has a ratings scale for compatibility between hearing aids and phones:

  • When operating in acoustic (Microphone) mode, the ratings are from M1 (worst) to M4 (best).
  • When operating in electromagnetic (Telecoil) mode, the ratings are from T1 (worst) to T4 (best).

The best possible rating is M4/T4 meaning that the phone works well in both modes. Devices rated below M3 are unsatisfactory for people with hearing aids.

Computer programs that allow the creation of a hearing aid using a PC, tablet or smartphone are currently gaining in popularity. Modern mobile devices have all the necessary components to implement this: hardware (an ordinary microphone and headphones may be used) and a high-performance microprocessor that carries digital sound processing according to a given algorithm. Application configuration is carried out by the user themselves in accordance with the individual features of their hearing ability. The computational power of modern mobile devices is sufficient to produce the best sound quality. This, coupled with software application settings (for example, profile selection according to a sound environment) provides for high comfort and convenience of use. In comparison with the digital hearing aid, mobile applications have the following advantages:

  • acoustic gain is up to 30 dB (with a standard headset);
  • complete invisibility (smartphone is not associated with a hearing aid);
  • ease of use (no need to use additional devices, batteries and so on.);
  • Fast switching between the external headset and phone microphone;
  • free distribution of applications.
  • High duration of the battery;
  • high sampling frequency (44.1 kHz) providing for excellent sound quality;
  • high wearing comfort;
  • low delay in audio processing (from 6,3 to 15,7 ms – depending on the mobile device model);
  • No loss of settings when switching from one gadget to another and back again;
  • No need to get used to it, when changing mobile devices;
  • user-friendly interface of software settings;

It should be clearly understood that "hearing aid" application for smartphone / tablet cannot be considered a complete substitution of a digital hearing aid, since the latter:

  • is a medical device (exposed to the relevant procedures of testing and certification);
  • is adjusted using audiometry procedures.
  • is designed for use by doctor's prescription;

Functionality of hearing aid applications may involve a hearing test (in situ audiometry) too. However, the results of the test are used only to adjust the device for comfortable working with the application. The procedure of hearing testing in any way cannot claim to replace an audiometry test carried out by a medical specialist, so cannot be a basis for diagnosis.

  • Apps such as Oticon ON for certain iOS (Apple) and Android devices can assist in locating a lost/misplaced hearing aid.

Wireless

Recent hearing aids include wireless hearing aids. One hearing aid can transmit to the other side so that pressing one aid's program button simultaneously changes the other aid, so that both aids change background settings simultaneously. FM listening systems are now emerging with wireless receivers integrated with the use of hearing aids. A separate wireless microphone can be given to a partner to wear in a restaurant, in the car, during leisure time, in the shopping mall, at lectures, or during religious services. The voice is transmitted wirelessly to the hearing aids eliminating the effects of distance and background noise. FM systems have shown to give the best speech understanding in noise of all available technologies. FM systems can also be hooked up to a TV or a stereo.

2.4 gigahertz Bluetooth connectivity is the most recent innovation in wireless interfacing for hearing instruments to audio sources such as TV streamers or Bluetooth enabled mobile phones. Current hearing aids generally do not stream directly via Bluetooth but rather do so through a secondary streaming device (usually worn around the neck or in a pocket), this bluetooth enabled secondary device then streams wirelessly to the hearing aid but can only do so over a short distance. This technology can be applied to ready-to-wear devices (BTE, Mini BTE, RIE, etc.) or to custom made devices that fit directly into the ear.

In developed countries FM systems are considered a cornerstone in the treatment of hearing loss in children. More and more adults discover the benefits of wireless FM systems as well, especially since transmitters with different microphone settings and Bluetooth for wireless cell phone communication have become available.

Many theatres and lecture halls are now equipped with assistive listening systems that transmit the sound directly from the stage; audience members can borrow suitable receivers and hear the program without background noise. In some theatres and churches FM transmitters are available that work with the personal FM receivers of hearing instruments.

Directional microphone

Most older hearing aids have only an omnidirectional microphone. An omnidirectional microphone amplifies sounds equally from all directions. In contrast, a directional microphone amplifies sounds from one direction more than sounds from other directions. This means that sounds originating from the direction the system is steered toward are amplified more than sounds coming from other directions. If the desired speech arrives from the direction of steering and the noise is from a different direction, then compared to an omnidirectional microphone, a directional microphone provides a better signal-to-noise ratio. Improving the signal-to-noise ratio improves speech understanding in noise. Directional microphones have been found to be the second best method to improve the signal-to-noise ratio (the best method was an FM system, which locates the microphone near the mouth of the desired talker).

Many hearing aids have both an omnidirectional and a directional microphone mode. This is because the wearer may not need or desire the noise-reducing properties of the directional microphone in a given situation. Typically, the omnidirectional microphone mode is used in quiet listening situations (e.g. living room) whereas the directional microphone is used in noisy listening situations (e.g. restaurant). The microphone mode is typically selected manually by the wearer. Some hearing aids automatically switch the microphone mode.

Adaptive directional microphones automatically vary the direction of maximum amplification or rejection (to reduce an interfering directional sound source). The direction of amplification or rejection is varied by the hearing aid processor. The processor attempts to provide maximum amplification in the direction of the desired speech signal source or rejection in the direction of the interfering signal source. Unless the user manually temporarily switches to a "restaurant program, forward only mode" adaptive directional microphones frequently amplify the speech of other talkers in a cocktail party type environments, such as restaurants or coffee shops; this can also be helpful during business meetings. The presence of multiple speech signals makes it difficult for the processor to correctly select the desired speech signal. Another disadvantage is that some noises often contain characteristics similar to speech, making it difficult for the hearing aid processor to distinguish the speech from the noise. Despite the disadvantages, adaptive directional microphones can provide improved speech recognition in noise.

FM systems have been found to provide a better signal-to-noise ratio even at larger speaker-to-talker distances in simulated testing conditions.

Telecoil

Main article: Audio induction loop

Telecoils or T-coils (from "Telephone Coils") are small devices installed in hearing aids or cochlear implants. An audio induction loop generates an electromagnetic field that can be detected by T-coils, allowing audio sources to be directly connected to a hearing aid. The T-coil is intended to help the wearer filter out background noise. They can be used with telephones, FM systems (with neck loops), and induction loop systems (also called "hearing loops") that transmit sound to hearing aids from public address systems and TVs. In the UK and the Nordic countries, hearing loops are widely used in churches, shops, railway stations, and other public places. In the US, telecoils and hearing loops are gradually becoming more common. Audio induction loops, telecoils and hearing loops are gradually becoming more common also in Slovenia.

A T-coil consists of a metal core (or rod) around which ultra-fine wire is coiled. T-coils are also called induction coils because when the coil is placed in a magnetic field, an alternating electric current is induced in the wire (Ross, 2002b; Ross, 2004). The T-coil detects magnetic energy and transduces (converts) it to electrical energy. In the United States, the Telecommunications Industry Association's TIA-1083 standard, specifies how analog handsets can interact with telecoil devices, to ensure the optimal performance.

Although T-coils are effectively a wide-band receiver, interference is unusual in most hearing loop situations. Interference can manifest as a buzzing sound, which varies in volume depending on the distance the wearer is from the source. Sources are electromagnetic fields, such as CRT computer monitors, older fluorescent lighting, some dimmer switches, many household electrical appliances and airplanes.

The states of Florida and Arizona have passed legislation that requires hearing professionals to inform patients about the usefulness of telecoils.

Legislation affecting use

In the United States, the Hearing Aid Compatibility Act of 1988 requires that the Federal Communications Commission (FCC) ensure that all telephones manufactured or imported for use in the United States after August 1989, and all "essential" telephones, be hearing aid-compatible (through the use of a telecoil).

"Essential" phones are defined as "coin-operated telephones, telephones provided for emergency use, and other telephones frequently needed for use by persons using such hearing aids." These might include workplace telephones, telephones in confined settings (like hospitals and nursing homes), and telephones in hotel and motel rooms. Secure telephones, as well as telephones used with public mobile and private radio services, are exempt from the HAC Act. "Secure" phones are defined as "telephones that are approved by the U.S. Government for the transmission of classified or sensitive voice communications."

In 2003, the FCC adopted rules to make digital wireless telephones compatible with hearing aids and cochlear implants. Although analog wireless phones do not usually cause interference with hearing aids or cochlear implants, digital wireless phones often do because of electromagnetic energy emitted by the phone's antenna, backlight, or other components. The FCC has set a timetable for the development and sale of digital wireless telephones that are compatible with hearing aids. This effort promises to increase the number of digital wireless telephones that are hearing aid-compatible. Older generations of both cordless and mobile phones used analog technology.

Audio boot

A hearing aid with an audio boot

An audio boot or audio shoe is an electronic device used with hearing aids; hearing aids often come with a special set of metal contacts for audio input. Typically the audio boot will fit around the end of the hearing aid (a behind-the-ear model, as in-the-ear do not afford any purchase for the connection) to link it with another device, like an FM system or a cellphone or even a digital audio player.

Direct audio input

A direct audio input connector
A DAI plug on the end of a cable

Direct audio input (DAI) allows the hearing aid to be directly connected to an external audio source like a CD player or an assistive listening device (ALD). By its very nature, DAI is susceptible to far less electromagnetic interference, and yields a better quality audio signal as opposed to using a T-coil with standard headphones. An audio boot is a type of device that may be used to facilitate DAI.

Processing

Every electronic hearing aid has at minimum a microphone, a loudspeaker (commonly called a receiver), a battery, and electronic circuitry. The electronic circuitry varies among devices, even if they are the same style. The circuitry falls into three categories based on the type of audio processing (analog or digital) and the type of control circuitry (adjustable or programmable). Hearing aid devices generally do not contain processors strong enough to process complex signal algorithms for sound source localization.

Analog

Analog audio may have:

  • Adjustable control: The audio circuit is analog with electronic components that can be adjusted. The hearing professional determines the gain and other specifications required for the wearer, and then adjusts the analog components either with small controls on the hearing aid itself or by having a laboratory build the hearing aid to meet those specifications. After the adjustment the resulting audio does not change any further, other than overall loudness that the wearer adjusts with a volume control. This type of circuitry is generally the least flexible. The first practical electronic hearing aid with adjustable analog audio circuitry was based on US Patent 2,017,358, "Hearing Aid Apparatus and Amplifier" by Samual Gordon Taylor, filed in 1932.
  • Programmable control: The audio circuit is analog but with additional electronic control circuitry that can be programmed by an audiologist, often with more than one program. The electronic control circuitry can be fixed during manufacturing or in some cases, the hearing professional can use an external computer temporarily connected to the hearing aid to program the additional control circuitry. The wearer can change the program for different listening environments by pressing buttons either on the device itself or on a remote control or in some cases the additional control circuitry operates automatically. This type of circuitry is generally more flexible than simple adjustable controls. The first hearing aid with analog audio circuitry and automatic digital electronic control circuitry was based on US Patent 4,025,721, "Method of and means for adaptively filtering near-stationary noise from speech" by D Graupe, GD Causey, filed in 1975. This digital electronic control circuitry was used to identify and automatically reduce noise in individual frequency channels of the analog audio circuits and was known as the Zeta Noise Blocker.

Digital

Block diagram of digital hearing aid

Digital audio, programmable control: Both the audio circuit and the additional control circuits are fully digital. The hearing professional programs the hearing aid with an external computer temporarily connected to the device and can adjust all processing characteristics on an individual basis. Fully digital circuitry allows implementation of many additional features not possible with analog circuitry, can be used in all styles of hearing aids and is the most flexible; for example, digital hearing aids can be programmed to amplify certain frequencies more than others, and can provide better sound quality than analog hearing aids. Fully digital hearing aids can be programmed with multiple programs that can be invoked by the wearer, or that operate automatically and adaptively. These programs reduce acoustic feedback (whistling), reduce background noise, detect and automatically accommodate different listening environments (loud vs. soft, speech vs. music, quiet vs. noisy, etc.), control additional components such as multiple microphones to improve spatial hearing, transpose frequencies (shift high frequencies that a wearer may not hear to lower frequency regions where hearing may be better), and implement many other features. Fully digital circuitry also allows control over wireless transmission capability for both the audio and the control circuitry. Control signals in a hearing aid on one ear can be sent wirelessly to the control circuitry in the hearing aid on the opposite ear to ensure that the audio in both ears is either matched directly or that the audio contains intentional differences that mimic the differences in normal binaural hearing to preserve spatial hearing ability. Audio signals can be sent wirelessly to and from external devices through a separate module, often a small device worn like a pendant and commonly called a "streamer", that allows wireless connection to yet other external devices. This capability allows optimal use of mobile telephones, personal music players, remote microphones and other devices. With the addition of speech recognition and internet capability in the mobile phone, the wearer has optimal communication ability in many more situations than with hearing aids alone. This growing list includes voice activated dialing, voice activated software applications either on the phone or on the internet, receipt of audio signals from databases on the phone or on internet, or audio signals from television sets or from global positioning systems. The first practical, wearable, fully digital hearing aid was invented by Maynard Engebretson, Robert E Morley Jr. and Gerald R Popelka. Their work resulted in US Patent 4,548,082, "Hearing aids, signal supplying apparatus, systems for compensating hearing deficiencies, and methods" by A Maynard Engebretson, Robert E Morley Jr. and Gerald R Popelka, filed in 1984. This patent formed the basis of all subsequent fully digital hearing aids from all manufacturers, including those produced currently.

The signal processing is performed by the microprocessor in real time and taking into account the individual preferences of the user (for example, increasing bass for better speech perception in noisy environments, or selective amplification of high frequencies for people with reduced sensibility to this range). The microprocessor automatically analyzes the nature of the external background noise and adapts the signal processing to the specific conditions (as well as to its change, for example, when the user goes outside from the building).

In speech enhancement, for example using neural networks, finds application in hearing aids. Problems may arise if these methods filter out emergency sounds such as fire alarms and car horns.

Difference between digital and analog hearing aids

Analogue hearing aids make all the sounds picked up by the microphone louder. For example, speech and ambient noise will be made louder together. On the other hand, digital hearing aid (DHA) technology processes the sound using digital technology. Before transmitting the sound to the speaker, the DHA microprocessor processes the digital signal received by the microphone according to an algorithm. This allows certain-frequency sounds to be made louder according to the individual user's settings (personal audiogram), and the DHA can automatically adjust to various environments (noisy streets, quiet room, concert hall, etc.).

For users with varying degrees of hearing loss, it is difficult to perceive the entire frequency range of external sounds. DHAs with multi-channel digital processing allow a user to "compose" the output sound by fitting a whole spectrum of the input signal into it. This gives users with limited hearing abilities the opportunity to perceive the whole range of ambient sounds, despite the personal difficulties of perception of certain frequencies. Moreover, even in this "narrow" range the DHA microprocessor is able to emphasize desired sounds (e.g. speech), lowering unwanted loud, high, etc., sounds at the same time.

According to research DHAs have a number of significant advantages compared to analogue hearing aids:

  • "Self-learning" and adaptive adjustment. They can implement adaptive selection of amplification parameters and processing.
  • Effective acoustic feedback reduction. The acoustic whistling common to all hearing aids can be adaptively controlled.
  • Effective use of directional microphones. Directional microphones can be adaptively controlled.
  • Extended frequency range. A larger range of frequencies can be implemented with frequency shifting.
  • Flexibility in selective amplification. They can provide more flexibility in frequency specific amplification to match the individual hearing characteristics of the user.
  • Improved connection to other devices. Connection to other devices such as smartphones and televisions is possible.
  • Noise reduction. They can reduce the background noise level to increase user comfort in noisy environments.
  • Speech recognition. They can distinguish the speech signal from the overall spectrum of sounds, which facilitates speech perception.

These advantages of DHAs were confirmed by a number of studies relating to the comparative analysis of digital hearing aids of second and first generations and analog hearing aids.

Difference between digital hearing aids and hearing aid applications

Smartphones have all the necessary hardware to perform the functions of a digital hearing aid: microphone, AD converter, digital processor, DA converter, amplifier, and speakers. External microphone and speakers can also be connected as a special headset.

The operational principles of hearing aid applications correspond to general operational principles of digital hearing aids: the microphone perceives an acoustic signal and converts it to digital form. Sound amplification is achieved through hardware and software in accordance with the user's hearing characteristics. Then, the signal is converted to analog form and received in the headphones by the user. The signal is processed in real time.

Stereo headsets with two speakers can be used, which allows separate binaural hearing correction for the left and right ear.

Unlike digital hearing aids, the adjustment of hearing aid applications is an integral part of the application itself. Hearing aid applications are adjusted in accordance with the user's audiogram. The whole adjustment process is automated so that the user can perform audiometry on their own.

The hearing correction application has two modes: audiometry and correction. In the audiometry mode, hearing thresholds are measured. In the correction mode, the signal is processed with respect to the obtained thresholds.

Hearing aid applications also provide for different computational formulas for the calculation of sound amplification based on the audiometry data. These formulas are intended for maximum comfortable speech amplification and best sound intelligibility.

Hearing aid applications allow the user to save different user profiles for different acoustic environments. Thus, in contrast to the static settings of digital hearing aids, the user can quickly switch between the profiles depending on the acoustic environment.

One of the most important characteristics of the hearing aid is acoustic feedback. In hearing aid applications, there is a significant hardware delay, so hearing aid applications use a signal processing scheme with the minimum possible algorithmic delay to make it as short as possible.

Difference between PSAP and digital hearing aids

Personal sound amplification products (PSAP) are classified by the FDA as "personal sound amplification devices". These compact electronic devices are designed for people without hearing loss. Unlike hearing aids (which the FDA classifies as devices to compensate for hearing impairment), the use of PSAP does not require a medical prescription. Such devices are used by hunters, naturalists (for audio observation of animals or birds), ordinary people (for example, to increase the volume of the TV in a quiet room), etc. PSAP models differ significantly in price and functionality. Some devices simply amplify sound. Others contain directional microphones, equalizers to adjust the audio signal gain and filter noise. In modern days, some people refer to these devices as OTC hearing aids.

Evolution of hearing aid applications

There are audio players designed specifically for the hard-of-hearing. These applications amplify the volume of the reproduced audio signal in accordance with the user's hearing characteristics and act as a music volume amplifier and assistive hearing aid. The amplification algorithm works on the frequencies that the user hears worse, thus restoring natural hearing perception of the sound of music.

Just as in hearing aid applications, the player adjustment is based on the user's audiogram.

There are also applications that not only adapt the sound of music but also include some hearing aid functions. Such applications include a sound amplification mode in accordance with the user's hearing characteristics as well as a noise suppression mode and a mode allowing the user to hear ambient sound without pausing the music.

Also, some applications allow the hard-of-hearing to watch video and listen to the radio with comfort. The operational principles of these applications are similar to those of hearing aid applications: the audio signal is amplified on the frequencies that the user hears worse.

Hearing aid adaptation

A person using a hearing aid for the first time often cannot make use of all its advantages quickly. The structure and characteristics of hearing aids are thoroughly devised by specialists in order to make the adjustment period as simple and quick as possible. However, despite this, a beginning hearing aid user certainly needs time to get used to it.

The process of adjusting to hearing prostheses consists of the following steps:

  • Initial adjustment of the device
  • Fine adjustments
  • Adaptation to the new sound

Due to the plasticity of the central nervous system, inactive hearing centers in the brain's cortex switch over to processing auditory stimuli in another frequency and intensity. The brain starts to perceive sounds amplified by the hearing aid immediately after the initial adjustment; however, it may not process them correctly right away.

Feeling the hearing aid in the ear may seem unusual. It also takes time to adapt to a new way of hearing. The ear has to be gradually adjusted to the new sound. The sound may seem unnatural, metallic, too loud or too quiet. A whistling sound may also appear, which can be unpleasant.

Hearing aids do not provide immediate improvement. The adjustment period can last from several hours to several months.

Patients are offered an initial schedule to wear their hearing aid, ensuring gradual adaptation to it. If the patient wears the hearing aid continually from the beginning, the unfamiliar sound may cause a headache, and as a result, the user may refuse to wear a hearing aid despite the fact that it helps. Audiologists often run a quick preparation course for the patients. As a rule, users have inflated expectations of hearing aids. They expect that hearing aids will help them to hear in the same way as before hearing loss, but it is not the case. Training sessions help hearing aid users to get accustomed to the feeling of new sounds. Users are strongly recommended to regularly visit an audiologist, including for the purposes of additional hearing aid adjustment.

Hearing aid applications, in contrast to traditional hearing aids, allow the implementation of options such as a built-in adaptation course.

The functions of the course may include:

  • control of the amount of time spent on learning;
  • control over the sequence of exercises;
  • daily reminders to do the exercises.

The goal of the course is to help a user adapt to using a hearing aid application.

The adaptation course includes a certain number of stages, starting from listening to a set of low everyday sounds in a quiet environment, getting accustomed to one's own speech and other people's speech, getting accustomed to speech among background noise, etc.

History

Main article: History of hearing aids
Madame de Meuron with ear trumpet

The first hearing aids were ear trumpets, and were created in the 17th century. Some of the first hearing aids were external hearing aids. External hearing aids directed sounds in front of the ear and blocked all other noises. The apparatus would fit behind or in the ear.

The movement toward modern hearing aids began with the creation of the telephone, and the first electric hearing aid, the "akouphone", was created about 1895 by Miller Reese Hutchison. By the late 20th century, digital hearing aids were commercially available.

The invention of the carbon microphone, transmitters, digital signal processing chip or DSP, and the development of computer technology helped transform the hearing aid to its present form.

History of digital aids

The history of DHA can be divided into three stages. The first stage began in the 1960s with the widespread use of digital computers for simulation of audio processing and for the analysis of systems and algorithms. The work was conducted with the help of the very large digital computers of that era. These efforts were not actual digital hearing aids because the computers were not fast enough for audio processing in real time and their size prevented them from being described as wearable, but they allowed successful studies of the various hardware circuits and algorithms for digital processing of audio signals. The software package Block of Compiled Diagrams (BLODI) developed by Kelly, Lockbaum and Vysotskiy in 1961 allowed simulation of any sound system that could be characterized in the form of a block diagram. A special phone was created so that a person with a hearing impairment could listen to the digitally processed signals, but not in real time. In 1967, Harry Levitt used BLODI to simulate a hearing aid on a digital computer.

Almost ten years later the second stage began with the creation of the hybrid hearing aid, in which the analog components of a conventional hearing aid consisting of amplifiers, filters and signal limiting were combined with a separate digital programmable component in a conventional hearing aid case. The audio processing remained analog but it was controlled by the digital programmable component. The digital component could be programmed by connecting the device to an external computer in the laboratory then disconnected to allow the hybrid device to function as a conventional wearable hearing aid.

The hybrid device was effective from a practical point of view because of the low power consumption and compact size. At that time, low-power analog amplifier technology was well developed in contrast to the available semiconductor chips able to process digital audio in real time. The combination of high performance analog components for real time audio processing and a separate low power digital programmable component only for controlling the analog signal led to the creation of several low power digital programmable components able to implement different types of control.

A hybrid hearing aid was developed by Etymotic Design. A little later, Mangold and Lane created a programmable multi-channel hybrid hearing aid. Graupe with co-authors developed a digital programmable component that implemented an adaptive noise filter.

The third stage began in the early 1980s by a research group at Central Institute for the Deaf headed up by faculty members at Washington University in St. Louis MO. This group created the first fully digital wearable hearing aid. They first conceived a complete, comprehensive full digital hearing aid, then designed and fabricated, miniaturized full digital computer chips using custom digital signal processing chips with low power and very large scale integrated (VLSI) chip technology able to process both the audio signal in real time and the control signals, yet able to be powered by a battery and be fully wearable as a full digital wearable hearing aid able to be actually used by individuals with hearing loss in real-world environments. Engebretson, Morley and Popelka were the inventors of the first full digital hearing aid. Their work resulted in US Patent 4,548,082, "Hearing aids, signal supplying apparatus, systems for compensating hearing deficiencies, and methods" by A Maynard Engebretson, Robert E Morley Jr. and Gerald R Popelka, filed in 1984 and issued in 1985. This full digital wearable hearing aid also included many additional features now used in all contemporary full digital hearing aids including a bidirectional interface with an external computer, self-calibration, self-adjustment, wide bandwidth, digital programmability, a fitting algorithm based on audibility, internal storage of digital programs, and fully digital multichannel amplitude compression and output limiting. This group created several of these full digital hearing aids and used them for research on hearing impaired people as they wore them in the same manner as conventional hearing aids in real-world situations. In this first full DHA all stages of sound processing and control were carried out in binary form. The external sound was picked up by a microphone positioned in an ITE ear module to take advantage of the acoustic effects of the pinna, then converted into binary code, digitally processed and digitally controlled in real time, then converted back to an analog signal sent to two miniature loudspeakers positioned in the same ITE ear module. The ITE module also contained an inward facing microphone to measure the sound actually generated in the ear canal, a precursor to separate probe tube measures now routinely used for hearing aid fitting. The necessary electronic components, including batteries, to support this arrangement were situated in a BTE module that could be supplemented with a body worn module. These specialized hearing aid chips continued to become smaller, increase in computational ability and require even less power. Now, virtually all commercial hearing aids are fully digital and their digital signal processing capability has significantly increased. Very small and very low power specialized digital hearing aid chips are now used in all hearing aids manufactured worldwide. Many additional new features also have been added with various on-board advanced wireless technology.

Regulation

Canada

Hearing aids are Class II regulated medical devices under Canada's Food and Drugs Act.

Under Health Canada, the Medical Devices Directorate (MDD) regulates the safety, quality, and effectiveness of hearing aids. All hearing aids imported and sold in Canada are subject to a pre-market review. Post-market, Health Canada monitors the performance of the hearing aid and any consumer complaints.

Hearing aid financial assistance is available at both the federal and provincial level. Provincial hearing aid assistance and coverage can vary widely depending on the province and territory.

In Canada, a prescription is required to purchase hearing aids. Only licensed audiologists, Ear, Nose and Throat (ENT) doctors, hearing instrument practitioners (where the profession exists), and audioprothésistes (in Quebec) can prescribe hearing aids. Over-the-counter (OTC) hearing aids are currently not available for sale in Canada.

Canadian taxpayers can claim tax relief for hearing aids as a medical expense.

Ireland

Like much of the Irish health care system, hearing aid provision is a mixture of public and private.

Hearing aids are provided by the state to children, OAPs and to people whose income is at or below that of the state pension. The Irish state hearing aid provision is extremely poor; people often have to wait for two years for an appointment.

It is estimated that the total cost to the state of supplying one hearing aid exceeds €2,000.

Hearing aids are also available privately, and there is grant assistance available for insured workers. For the fiscal year ending 2016, the grant stands at a maximum of €500 per ear.

Irish taxpayers can also claim tax relief at the standard rate as hearing aids are recognised as a medical device.

Hearing aids in the Republic of Ireland are exempt from VAT.

Hearing aid providers in Ireland mostly belong to the Irish Society of Hearing Aid Audiologists.

United States

Ordinary hearing aids are Class I regulated medical devices under Federal Food and Drug Administration (FDA) rules. A 1976 statute explicitly prohibits any state requirement that is "different from, or in addition to, any requirement applicable" to regulated medical devices (which includes hearing aids) which relates "to the safety and effectiveness of the device". Inconsistent state regulation is preempted under the federal law. In the late 1970s, the FDA established federal rules governing hearing aid sales, and addressed various requests by state authorities for exemptions from federal preemption, granting some and denying others. The Over-the-Counter Hearing Aid Act (OTC Act) was passed under the FDA Reauthorization Act of 2017, creating a class of hearing aids regulated by the FDA available directly to consumers without involvement from a licensed professional. This law's provisions are expected to go into effect in 2020.

In August 2022, the FDA issued a final rule to improve access to hearing aids. The action establishes a new category of over-the-counter (OTC) hearing aids, enabling consumers with perceived mild to moderate hearing impairment to purchase hearing aids directly from stores or online retailers without the need for a medical exam, prescription or a fitting adjustment by an audiologist. The FDA action amends existing rules that apply to prescription hearing aids for consistency with the new OTC category, it repeals the conditions for sale for hearing aids, and it includes provisions that address some of the effects of the FDA OTC hearing aid regulations on state regulation of hearing aids. The FDA also issued the final guidance, Regulatory Requirements for Hearing Aid Devices and Personal Sound Amplification Products (PSAPs), to clarify the differences between hearing aids, which are medical devices, and PSAPs, consumer products that help people with normal hearing amplify sounds.

Cost

A store called "Bonavox Hearing Aids," on a brick road and next to two other businesses.
Hearing aid shop, Dublin, Ireland

Several industrialized countries supply free or heavily discounted hearing aids through their publicly funded health care system.

Australia

The Australian Department of Health and Ageing provides eligible Australian citizens and residents with a basic hearing aid free-of-charge, though recipients can pay a "top up" charge if they wish to upgrade to a hearing aid with more or better features. Maintenance of these hearing aids and a regular supply of batteries is also provided, on payment of a small annual maintenance fee.

Canada

In Canada, health care is a responsibility of the provinces. In the province of Ontario, the price of hearing aids is partially reimbursed through the Assistive Devices Program of the Ministry of Health and Long-Term care, up to $500 for each hearing aid. Like eye appointments, audiological appointments are no longer covered through the provincial public health plan. Audiometric testing can still easily be obtained, often free of charge, in private sector hearing aid clinics and some ear, nose and throat doctors offices. Hearing aids may be covered to some extent by private insurance or in some cases through government programs such as Veterans Affairs Canada or Workplace Safety & Insurance Board.

Iceland

Social Insurance pays a one time fee of ISK 30,000 for any kind of hearing aid. However, the rules are complicated and require that both ears have significant hearing loss in order to qualify for reimbursement. BTE hearing aids range from ISK 60,000 to ISK 300,000.

India

In India hearing aids of all kinds are easily available. Under central and state government health services, the poor can often avail themselves of free hearing devices. However, market prices vary for others and can range from Rs 10,000 to Rs 275,000 per ear.

United Kingdom

From 2000 to 2005 the Department of Health worked with Action on Hearing Loss (then called RNID) to improve the quality of NHS hearing aids so every NHS audiology department in England was fitting digital hearing aids by March 2005. By 2003 over 175,000 NHS digital hearing aids had been fitted to 125,000 people. Private companies were recruited to enhance the capacity, and two were appointed – David Ormerod Hearing Centres, partly owned by Alliance Boots and Ultravox Group, a subsidiary of Amplifon.

Within the UK, the NHS provides digital BTE hearing aids to NHS patients, on long-term loan, free of charge. Other than BAHAs (bone anchored hearing aid) or cochlear implants, where specifically required, BTEs are usually the only style available. Private purchases may be necessary if a user desires a different style. Batteries are free.

In 2014 the Clinical Commissioning Group in North Staffordshire considered proposals to end provision of free hearing aids for adults with mild to moderate age related hearing loss, which currently cost them £1.2m a year. Action on Hearing Loss mobilised a campaign against the proposal.

In June 2018 the National Institute for Health and Care Excellence produced new guidance saying that hearing aids should be offered at the first opportunity when hearing loss affects the individual's ability to hear and communicate, rather than waiting for arbitrary thresholds of hearing loss to be reached.

United States

Most private healthcare providers in the United States do not provide coverage for hearing aids, so all costs are usually borne by the recipient. The cost for a single hearing aid can vary between $500 and $6,000 or more, depending on the level of technology and whether the clinician bundles fitting fees into the cost of the hearing aid. Though if an adult has hearing loss which substantially limits major life activities, some state-run vocational rehabilitation programs can provide upwards of full financial assistance. Severe and profound hearing loss often falls within the "substantially limiting" category. Less expensive hearing aids can be found on the internet or mail order catalogs, but most in the under-$200 range tend to amplify the low frequencies of background noise, making it harder to hear the human voice.

Military veterans receiving VA medical care are eligible for hearing aids based on medical need. The Veterans Administration pays the full cost of testing and hearing aids to qualified military veterans. Major VA medical facilities provide complete diagnostic and audiology services.

The cost of hearing aids is a tax-deductible medical expense for those who itemize medical deductions.

Research involving more than 40,000 US households showed a convincing correlation between the degree of hearing loss and the reduction of personal income. According to the same research, hearing aids were shown to mitigate the impact of income loss by 90%–100% for those with milder hearing losses and from 65%–77% for those with severe to moderate hearing loss.

Batteries

While there are some instances that a hearing aid uses a rechargeable battery or a long-life disposable battery, the majority of modern hearing aids use one of five standard button cell zinc–air batteries. (Older hearing aids often used mercury battery cells, but these cells have become banned in most countries today.) Modern hearing aid button cell types are typically referred to by their common number name or the color of their packaging.

They are typically loaded into the hearing aid via a rotating battery door, with the flat side (case) as the positive terminal (cathode) and the rounded side as the negative terminal (anode).

These batteries all operate from 1.35 to 1.45 volts.

The type of battery a specific hearing aid utilizes depends on the physical size allowable and the desired lifetime of the battery, which is in turn determined by the power draw of the hearing aid device. Typical battery lifetimes run between 1 and 14 days (assuming 16-hour days).

Hearing Aid Battery Types
Type/ Color Code Dimensions (Diameter×Height) Common Uses Standard Names Misc Names
675 11.6 mm × 5.4 mm High-Power BTEs, Cochlear implants IEC: PR44, ANSI: 7003ZD 675, 675A, 675AE, 675AP, 675CA, 675CP, 675HP, 675HPX, 675 Implant Plus, 675P (HP), 675PA, 675SA, 675SP, A675, A675P, AC675, AC675E, AC675E/EZ, AC675EZ, AC-675E, AP675, B675PA, B6754, B900PA, C675, DA675, DA675H, DA675H/N, DA675N, DA675X, H675AE, L675ZA, ME9Z, P675, P675i+, PR44, PR44P, PR675, PR675H, PR675P, PR-675PA, PZ675, PZA675, R675ZA, S675A, V675, V675A, V675AT, VT675, XL675, Z675PX, ZA675, ZA675HP
13 7.9 mm × 5.4 mm BTEs, ITEs IEC: PR48, ANSI: 7000ZD 13, 13A, 13AE, 13AP, 13HP, 13HPX, 13P, 13PA, 13SA, 13ZA, A13, AC13, AC13E, AC13E/EZ, AC13EZ, AC-13E, AP13, B13BA, B0134, B26PA, CP48, DA13, DA13H, DA13H/N, DA13N, DA13X, E13E, L13ZA, ME8Z, P13, PR13, PR13H, PR-13PA, PZ13, PZA13, R13ZA, S13A, V13A, VT13, V13AT, W13ZA, XL13, ZA13
312 7.9 mm × 3.6 mm miniBTEs, RICs, ITCs IEC: PR41, ANSI: 7002ZD 312, 312A, 312AE, 312AP, 312HP, 312HPX, 312P, 312PA, 312SA, 312ZA, AC312, AC312E, AC312E/EZ, AC312EZ, AC-312E, AP312, B312BA, B3124, B347PA, CP41, DA312, DA312H, DA312H/N, DA312N, DA312X, E312E, H312AE, L312ZA, ME7Z, P312, PR312, PR312H, PR-312PA, PZ312, PZA312, R312ZA, S312A, V312A, V312AT, VT312, W312ZA, XL312, ZA312
10 5.8 mm × 3.6 mm CICs, RICs IEC: PR70, ANSI: 7005ZD 10, 10A, 10AE, 10AP, 10DS, 10HP, 10HPX, 10SA, 10UP, 20PA, 230, 230E, 230EZ, 230HPX, AC10, AC10EZ, AC10/230, AC10/230E, AC10/230EZ, AC230, AC230E, AC230E/EZ, AC230EZ, AC-230E, AP10, B0104, B20BA, B20PA, CP35, DA10, DA10H, DA10H/N, DA10N, DA230, DA230/10, L10ZA, ME10Z, P10, PR10, PR10H, PR230H, PR536, PR-10PA, PR-230PA, PZA230, R10ZA, S10A, V10, VT10, V10AT, V10HP, V230AT, W10ZA, XL10, ZA10
5 5.8 mm × 2.1 mm CICs IEC: PR63, ANSI: 7012ZD 5A, 5AE, 5HPX, 5SA, AC5, AC5E, AP5, B7PA, CP63, CP521, L5ZA, ME5Z, P5, PR5H, PR-5PA, PR521, R5ZA, S5A, V5AT, VT5, XL5, ZA5

See also

Notes and references

  1. Although audioprothésistes are allowed to administer hearing tests, to prevents conflicts of interest, the healthcare system will no compensate hearing aids if the test was not performed by an audiologist.
  1. Bentler RA, Duve MR (December 2000). "Comparison of hearing aids over the 20th century". Ear and Hearing. 21 (6): 625–639. doi:10.1097/00003446-200012000-00009. PMID 11132788. S2CID 46218426.
  2. "Ear Horn Q&A". Archived from the original on 24 July 2008. Retrieved 6 December 2007.
  3. Kochkin S (January 2010). "MarkeTrak VIII: Consumer satisfaction with hearing aids is slowly increasing". The Hearing Journal. 63 (1): 19–20. doi:10.1097/01.HJ.0000366912.40173.76. S2CID 73880581.
  4. Cox RM, Johnson JA, Xu J (July 2016). "Impact of Hearing Aid Technology on Outcomes in Daily Life I: the Patients' Perspective". Ear and Hearing. 37 (4): e224–37. doi:10.1097/AUD.0000000000000277. PMC 4925253. PMID 26881981.
  5. "The Best Over-the-Counter Hearing Aids and Other Hearing Solutions". The New York Times. Archived from the original on 14 January 2023. Retrieved 5 December 2022.
  6. J. Moore; Brian C. (2007). Cochlear hearing loss: physiological, psychological and technical issues (2nd ed.). Chichester: John Wiley & Sons. ISBN 978-0-470-51633-1. OCLC 180765972.
  7. Bentler RA, Kramer SE (August 2000). "Guidelines for choosing a self-report outcome measure". Ear and Hearing. 21 (4 Suppl): 37S–49S. doi:10.1097/00003446-200008001-00006. PMID 10981593. S2CID 36628081.
  8. Taylor, Brian (22 October 2007). "Self-Report Assessment of Hearing Aid Outcome – An Overview". AudiologyOnline. Archived from the original on 29 January 2015. Retrieved 29 May 2013.
  9. Humes L, Humes L (April 2004). "Factors Affecting Long-Term Hearing Aid Success". Seminars in Hearing. 25 (1): 63–72. doi:10.1055/s-2004-823048. S2CID 260312035.
  10. Katz, Jack; Medwetsky, Larry; Burkard, Robert; Hood, Linda (2009). "Chapter 38, Hearing Aid Fitting for Adults: Selection, Fitting, Verification, and Validation". Handbook of Clinical Audiology (6th ed.). Baltimore MD: Lippincott Williams & Wilkins. p. 858. ISBN 978-0-7817-8106-0.
  11. Stach, Brad (2003). Comprehensive Dictionary of Audiology (2nd ed.). Clifton Park NY: Thompson Delmar Learning. p. 167. ISBN 978-1-4018-4826-2.
  12. "Tinnitus And Hearing Aids - Optimal Hearing Systems, The Hearing Aid Company - Since 1961". Optimal Hearing. 30 December 2016. Archived from the original on 6 July 2020. Retrieved 5 July 2020.
  13. Hartmann, William M. (14 September 2004). Signals, Sound, and Sensation. Springer Science & Business Media. pp. 72–. ISBN 978-1-56396-283-7. Archived from the original on 3 December 2016.
  14. ^ Hearing Aid Basics, National Institute of Health, archived from the original on 13 November 2011, retrieved 2 December 2011
  15. "Hearing Aids". National Institute on Deafness and Other Communication Disorders. Archived from the original on 15 September 2012. Retrieved 9 September 2012.
  16. ^ "Hearing Aid Buying Guide". Consumer Reports. February 2017. Archived from the original on 12 February 2017. Retrieved 13 February 2017.
  17. "Problems with hearing aids: Ask our audiologist – Action On Hearing Loss: RNID". Action On Hearing Loss. Archived from the original on 17 June 2016. Retrieved 28 December 2016.
  18. Sickel, K. (13 September 2007) Shortest Path Search with Constraints on Surface Models of In-ear Hearing Aids Archived 5 July 2017 at the Wayback Machine 52. IWK, Internationales Wissenschaftliches Kolloquium (Computer science meets automation Ilmenau 10.) Vol. 2 Ilmenau : TU Ilmenau Universitätsbibliothek 2007, pp. 221–226
  19. "Hearing Aids for Children". Hearing Aids for Children. American Speech-Language-Hearing Association. Archived from the original on 17 August 2022. Retrieved 1 December 2014.
  20. Eisenberg, Anne (24 September 2005) The Hearing Aid as Fashion Statement Archived 6 January 2016 at the Wayback Machine. NY Times.
  21. Dybala, Paul (6 March 2006) ELVAS Sightings – Hearing Aid or Headset Archived 16 August 2012 at the Wayback Machine. AudiologyOnline.com.
  22. Ross, Mark (January 2004) The "Occlusion Effect" – What it is, and What to Do About it Archived 15 February 2016 at the Wayback Machine, hearingresearch.org.
  23. Sickel, K. et al. (2009) "Semi-Automatic Manufacturing of Customized Hearing Aids Using a Feature Driven Rule-based Framework" Archived 4 March 2016 at the Wayback Machine. Proceedings of the Vision, Modeling, and Visualization Workshop 2009 (Braunschweig, Germany 16–18 November 2009), pp. 305–312
  24. "Invisible Hearing Aids or IIC hearing aids are convenient. Will they suit you?". EarGuru Ear Health Blog. 5 July 2018. Archived from the original on 17 August 2022. Retrieved 7 June 2021.
  25. Sanford MJ, Anderson T, Sanford C (March 2014). "The extended-wear hearing device: Observations on patient experiences and its integration into a practice". Hearing Review. 21 (3): 26–31. Archived from the original on 5 December 2014. Retrieved 1 December 2014.
  26. "128.030 | Collections Online". collections.thackraymuseum.co.uk. Retrieved 23 September 2024.
  27. "Concealed Hearing Devices of the 20th Century". Concealed Hearing Devices of the 20th Century. Bernard Becker Medical Library. Archived from the original on 23 January 2015. Retrieved 1 December 2014.
  28. "Why Don't They Made Hearing Aids Glasses Anymore". www.hearreview.com. Archived from the original on 1 August 2020. Retrieved 27 November 2018.
  29. Netherlands: Dutch Unveil 'Varibel' – The Eyeglasses That Hear Archived 15 April 2012 at the Wayback Machine, Publish Date: 1 March 2007, Related Company Website: www, varibel.nl. Accessed 10 February 2008.
  30. The manufacturer's website is published in Dutch and French at "Varibel.nl". Archived from the original on 22 February 2008. Retrieved 9 February 2016. and there is a TV news report in English at http://varibel.nl/site/Files/default.asp?iChannel=4&nChannel=Files
  31. "Mobile Medical Applications. Guidance for Industry and Food and Drug Administration Staff" (PDF). Food and Drug Administration. 2015. Archived (PDF) from the original on 23 January 2019. Retrieved 15 March 2019.
  32. ^ E.S. Azarov; M.I. Vashkevich; S.V. Kozlova; A.A. Petrovsky (2014). "Hearing correction system based on mobile computing platform (in Russian)". Informatics. 2 (42): 5–24. ISSN 1816-0301. Archived from the original on 29 March 2019. Retrieved 15 March 2019.
  33. ^ A. Vonlanthen; H. Arndt (2009). Hearing aids (in Russian). Translated by T, Gvelesiani. Rostov-on-Don: Feniks. ISBN 978-5-222-15490-8.
  34. Mestayer, Kathi. "Science is revealing how internal volume controls can influence our sensitivity to sound". Hearing Health. Archived from the original on 17 August 2022. Retrieved 17 August 2022.
  35. TIA-1083 Revision A, 17 November 2010 Archived 16 May 2012 at the Wayback Machine. ihs.com
  36. "New TIA Standard Will Improve Hearing Aid Compatibility with Digital Cordless Phones". U.S. Telecommunications Industry Association. 5 April 2007. Archived from the original on 6 December 2010. Retrieved 3 November 2011.
  37. "Приложение для смартфонов заменит глухим слуховой аппарат? – Глухих.нет. Новостной портал для глухих и слабослышащих | Новости мира глухих и слабослышащих | Сайт глухих | Спорт глухих | Can application substitute hearing aid?". gluxix.net. 13 March 2014. Archived from the original on 25 December 2014. Retrieved 18 February 2015.
  38. "Mobile Medical Applications". fda.gov. Archived from the original on 2 May 2013. Retrieved 18 February 2015.
  39. "Hearing aids, information on hearing loss and tinnitus | Oticon". www.oticon.global. Archived from the original on 27 September 2016. Retrieved 25 September 2016.
  40. Mroz, Mandy. "Hearing Aids and Bluetooth Technology". Hearing Aids and Bluetooth Technology. Healthy Hearing. Archived from the original on 9 November 2014. Retrieved 1 December 2014.
  41. Dave Fabry; Hans Mülder; Evert Dijkstra (November 2007). "Acceptance of the wireless microphone as a hearing aid accessory for adults". The Hearing Journal. 60 (11): 32–36. doi:10.1097/01.hj.0000299170.11367.24. S2CID 168059640.
  42. Hawkins DB (November 1984). "Comparisons of speech recognition in noise by mildly-to-moderately hearing-impaired children using hearing aids and FM systems". Journal of Speech and Hearing Disorders. 49 (4): 409–18. doi:10.1044/jshd.4904.409. PMID 6503247.
  43. Ricketts T, Henry P (March 2002). "Evaluation of an adaptive, directional-microphone hearing aid". International Journal of Audiology. 41 (2): 100–112. doi:10.3109/14992020209090400. PMID 12212855. S2CID 2035086.
  44. Lewis MS, Crandell CC, Valente M, Horn JE (June 2004). "Speech perception in noise: directional microphones versus frequency modulation (FM) systems". Journal of the American Academy of Audiology. 15 (6): 426–439. doi:10.3766/jaaa.15.6.4. PMID 15341224. Archived from the original on 27 November 2022. Retrieved 17 August 2022.
  45. TIA-1083: A NEW STANDARD TO IMPROVE CORDLESS PHONE USE FOR HEARING AID WEARERS Archived 25 April 2012 at the Wayback Machine. U.S. Telecommunications Industry Association
  46. "Public Law 100-394, [47 USC 610] – Hearing Aid Compatibility Act of 1988". PRATP. Archived from the original on 26 July 2010. Retrieved 8 June 2013.
  47. "Boot Definition". www.nchearingloss.org. Archived from the original on 3 March 2016. Retrieved 2 June 2017.
  48. "Boot Definition". www.nchearingloss.org. Archived from the original on 3 March 2016. Retrieved 2 June 2017.
  49. Ganguly Anshuman, Reddy Chandan, Hao Yiya, Panahi Issa (2016). "Improving Sound Localization for Hearing Aid Devices Using Smartphone Assisted Technology". 2016 IEEE International Workshop on Signal Processing Systems (SiPS). pp. 165–170. doi:10.1109/SiPS.2016.37. ISBN 978-1-5090-3361-4. S2CID 7603815.{{cite book}}: CS1 maint: multiple names: authors list (link)
  50. Heidtman, Laurel (28 September 2010). "Analog Vs. Digital Hearing Aids". LiveStrong.com. Archived from the original on 3 May 2012. Retrieved 23 July 2012.
  51. Levitt, Harry (26 December 2007). "Digital Hearing Aids". The ASHA Leader. Archived from the original on 17 July 2012. Retrieved 23 July 2012.
  52. "HIMPP History | HIMPP". Archived from the original on 24 December 2021. Retrieved 24 December 2021.
  53. "Как работают слуховые аппараты". radugazvukov.ru. Archived from the original on 25 December 2014. Retrieved 18 February 2015.
  54. Soha A. Nossier, Julie Wall1, Mansour Moniri, Cornelius Glackin, Nigel Cannings (18–22 September 2022). Convolutional Recurrent Smart Speech Enhancement Architecture for Hearing Aids (PDF). Interspeech 2022. Incheon, Korea. Archived (PDF) from the original on 20 November 2022. Retrieved 20 November 2022.{{cite conference}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  55. Janet McCaffrey (21 December 2009). "HJ0905 Kochkin copy" (PDF). The Hearing Journal. Archived from the original (PDF) on 4 March 2016. Retrieved 18 February 2015.
  56. "Fitting Tips: Essentials of Hearing Aid Selection, Part 1: Cosmetics Are Not Just What Meets the Ear – Hearing Review". hearingreview.com. 2 October 2003. Archived from the original on 18 February 2015. Retrieved 18 February 2015.
  57. Richard Preid Fotorotar AG (8 August 2007). "24_P54090_Pho_Kapitel_06bis07" (PDF). Archived from the original (PDF) on 18 February 2015. Retrieved 18 February 2015.
  58. "Hearing Review Three-Year Index 2003–2005 – Hearing Review". hearingreview.com. 6 December 2005. Archived from the original on 18 February 2015. Retrieved 18 February 2015.
  59. "Применение технологии широкополосного изменения огибающей спектра звукового сигнала Petralex® в онлайн-приложениях коррекции слуха::Журнал СА 7–8.2014 (Mann, Eric A., M.D., PhD, "Hearing Aids and Personal Sound Amplifiers: Know the Difference", U.S. Food and Drug Administration Consumer Updates website, Oct. 20, 2009. Retrieved 2013-05-23.)" (in Russian). samag.ru. Archived from the original on 25 December 2014. Retrieved 18 February 2015.
  60. Beck, Melinda, "Getting an Earful: Testing A Tiny, Pricey Hearing Aid" Archived 16 September 2017 at the Wayback Machine, The Wall Street Journal, 29 January 2008. Retrieved 23 May 2013.
  61. ^ "Адаптация к слуховому аппарату". r-sluh.ru (in Russian). Archived from the original on 28 May 2019. Retrieved 28 May 2019.
  62. ^ "Адаптация к слуховому аппарату". www.xn----ttbbfjpems.xn—p1ai (in Russian). Archived from the original on 28 May 2019. Retrieved 28 May 2019.
  63. Королева, Инна Васильевна (2012). Введение в аудиологию и слухопротезирование (in Russian). КАРО. ISBN 978-5-9925-0737-9. Archived from the original on 3 August 2020. Retrieved 29 May 2020.
  64. "Free apps help better hearing!". PETRALEX Hearing Aid. Archived from the original on 15 May 2018. Retrieved 28 May 2019.
  65. Mills, Mara (2011). "Hearing Aids and the History of Electronics Miniaturization". IEEE Annals of the History of Computing. 33 (2): 24–45. doi:10.1109/MAHC.2011.43. S2CID 10946285.
  66. Howard, Alexander (26 November 1998). "Hearing Aids: Smaller and Smarter." Archived 28 December 2016 at the Wayback Machine New York Times.
  67. ^ "LEVITT: Digital Hearing Aids: A Tutorial Review" (PDF). rehab.research.va.gov. Archived (PDF) from the original on 19 March 2015. Retrieved 18 February 2015.
  68. Kelly LJ Jr; Lochbaum C; Vyssotsky VA. A block diagram compiler. Bell System Tech J (40):669–676, 1961.
  69. Graupe D, Grosspietsch JK, Basseas SP. "A single microphone-based self-adaptive filter of noise from speech and its performance evaluation. J Rehabil Res Dev 24(4), 1987 (this issue" (PDF). rehab.research.va.gov. Archived (PDF) from the original on 24 September 2015. Retrieved 18 February 2015.
  70. Engebretson, AM, Popelka, GR, Morley, RE, Niemoeller, AF, and Heidbreder, AF: A digital hearing aid and computer-based fitting procedure. Hearing Instruments 1986; 37(2): 8-14
  71. Popelka, GR: Computer assisted hearing aid fitting, in Microcomputer Applications in Rehabilitation of Communication Disorders, M.L. Grossfeld and C.A. Grossfeld, Editors. 1986, Aspen Publishing: Rockville, Maryland. 67-95
  72. Popelka, GR., Moore, BJC, Popper, AN, and Fay, RR: 2016, Hearing Aids, Springer Science, LLC, NY, NY
  73. Canada, Health (29 July 2016). "Medical batteries". www.canada.ca. Archived from the original on 21 March 2023. Retrieved 21 March 2023.
  74. "Hearing aid financial assistance in Canada". Hearing Directory. Archived from the original on 21 March 2023. Retrieved 21 March 2023.
  75. Agency, Canada Revenue (4 January 2016). "Details of medical expenses". www.canada.ca. Archived from the original on 21 March 2023. Retrieved 21 March 2023.
  76. "Aural". Ireland Department of Social Protection. Archived from the original on 2 July 2012. Retrieved 23 July 2012.
  77. ^ 21 U.S.C. § 360k (a) (2005).
  78. Missouri Board of Examiners for Hearing Instrument Specialists v. Hearing Help Express, Inc., 447 3d 1033 (8th Cir. 2006)
  79. Final Rule issued in Docket 76N-0019, 42 FR 9286 (15 February 1977).
  80. Exemption from Preemption of State and Local Hearing Aid Requirements; Applications for Exemption, Docket No. 77N-0333, 45 FR 67326; Medical Devices: Applications for Exemption from Federal Preemption of State and Local hearing Aid Requirements, Docket No. 78P-0222, 45 FR 67325 (10 October 1980).
  81. "H.R.2430 - 115th Congress (2017-2018): FDA Reauthorization Act of 2017". www.congress.gov. 18 August 2017. Archived from the original on 22 February 2020. Retrieved 16 March 2020.
  82. ^ "FDA Finalizes Historic Rule Enabling Access to Over-the-Counter Hearing Aids for Millions of Americans". U.S. Food and Drug Administration (FDA). 16 August 2022. Archived from the original on 16 August 2022. Retrieved 16 August 2022. Public Domain This article incorporates text from this source, which is in the public domain.
  83. "Public Inspection: Medical Devices: Ear, Nose, and Throat Devices; Establishing Over-the-Counter Hearing Aids". Federal Register. U.S. Food and Drug Administration (FDA). 16 August 2022. Archived from the original on 16 August 2022. Retrieved 16 August 2022. Public Domain This article incorporates text from this source, which is in the public domain.
  84. "Regulatory Requirements for Hearing Aids and PSAPs Guidance". U.S. Food and Drug Administration (FDA). 12 August 2022. Archived from the original on 16 August 2022. Retrieved 16 August 2022. Public Domain This article incorporates text from this source, which is in the public domain.
  85. "Understanding the Australian Government Hearing Services Program". Archived from the original on 9 September 2007. Retrieved 4 December 2007.
  86. Social Insurance Administration – Iceland Accessed 30 November 2007 Archived 16 February 2008 at the Wayback Machine
  87. "Loud and clear". Health Service Journal. 18 December 2003. Archived from the original on 23 October 2014. Retrieved 17 October 2014.
  88. NHS hearing aid service fact sheet Accessed 26 November 2007 Archived 2 October 2010 at the Wayback Machine
  89. "Hearing aid charging opposed in feedback exercise". Health Service Journal. 23 September 2014. Archived from the original on 9 October 2014. Retrieved 17 October 2014.
  90. "Hearing loss in adults: assessment and management". NICE. 21 June 2018. Retrieved 5 July 2024.
  91. "Questions and Answers about Deafness and Hearing Impairments in the Workplace and the Americans with Disabilities Act". U.S. Equal Employment Opportunity Commission. Archived from the original on 4 March 2016. Retrieved 26 November 2007.
  92. Mahany, Barbara (9 March 2011). "Now Hear This". Chicago Tribune. Archived from the original on 15 June 2013.
  93. Romano, Tricia (22 October 2012). "The Hunt for an Affordable Hearing Aid". Well. New York Times. Archived from the original on 25 February 2015.
  94. "Topic 502 – Medical and Dental Expenses". Internal Revenue Service. Archived from the original on 3 July 2017. Retrieved 26 November 2007.
  95. Kochkin, Sergei (October 2010). "MarkeTrak VIII: The efficacy of hearing aids in achieving compensation equity in the workplace". The Hearing Journal. 63 (10): 19–24, 26, 28. doi:10.1097/01.HJ.0000389923.80044.e6. S2CID 52230904.


Further reading

External links

Portals: Categories: