Editing Bone conduction

{{Short description|Conduction of sound to the inner ear}}

'''Bone conduction''' is the [[wikt:conduction|conduction]] of [[sound]] to the [[inner ear]] primarily through the bones of the [[human skull|skull]], allowing the hearer to perceive audio content even if the ear canal is blocked. Bone conduction transmission occurs constantly as sound waves vibrate bone, specifically the bones in the skull, although it is hard for the average individual to distinguish sound being conveyed through the bone as opposed to the sound being conveyed through the air via the ear canal.  Intentional transmission of sound through bone can be used with individuals with normal hearing—as with bone-conduction headphones—or as a treatment option for certain types of hearing impairment. Bones are generally more effective at transmitting lower-frequency sounds compared to higher-frequency sounds.

Bone conduction is also called the second auditory pathway and not to be confused with [[cartilage conduction]], which is considered the third auditory pathway.

==Overview==
Bone conduction is one reason why a person's voice sounds different to them when it is recorded and played back. Because the skull conducts lower frequencies better than air, people perceive their own voices to be lower and fuller than others do, and a recording of one's own voice frequently sounds higher than one expects (see [[voice confrontation]]).<ref>{{cite web |author=Zhi Cai |author2=Alan G. Madsen |author3=Douglas G. Richards |author4=Martin L. Lenhardt |date=2002 |title=Response of Human Skull to Bone Conducted Sound in the Audiometric to Ultrasonic Range |url=https://docplayer.net/38615249-Response-of-human-skull-to-bone-conducted-sound-in-the-audiometric-ultrasonic-range.html |access-date=3 July 2013 |publisher=Virginia Commonwealth University}}</ref><ref>{{cite web |author=Brent Zupp |date=2003–2012 |title=Why Does Your Voice Sound Different on a Recording? |url=https://www.wanderings.net/notebook/Main/WhyDoesYourVoiceSoundDifferentRecordingPlayback |url-status=live |archive-url=https://web.archive.org/web/20241119203056/https://www.wanderings.net/notebook/Main/WhyDoesYourVoiceSoundDifferentRecordingPlayback |archive-date=2024-11-19 |access-date=3 July 2013 |work=Wanderings |publisher=Brent Zupp}}</ref>

Musicians may use bone conduction using a [[tuning fork]] while tuning stringed instruments. After the fork starts vibrating, placing it in the mouth with the stem between the back teeth ensures that one continues to hear the note via bone conduction, and both hands are free to do the tuning.<ref>{{cite book|title=Teach Yourself to Play Mandolin|url=https://books.google.com/books?id=1jFWy2qR4U4C&q=bone+conduction|publisher=Alfred Music Publishing|access-date=3 July 2015|author=Dan Fox|date=1996|isbn=978-0-7390-0286-5}}</ref> [[Ludwig van Beethoven]] was famously rumored to be using bone conduction after losing most of his hearing, by placing one end of a rod in his mouth and resting the other end on the rim of his piano.<ref>{{Cite web|url=http://www.goldendance.co.jp/English/boneconduct/01.html|title=Bone Conduction: How it Works|website=www.goldendance.co.jp|access-date=2018-11-13}}</ref>

It has also been observed that some animals can perceive sound and even communicate by sending and receiving vibration through bone.<ref>{{Cite web|url=https://news.stanford.edu/pr/01/elephants37.html|title=Elephants pick up good vibrations -- through their feet: 3/01|website=news.stanford.edu|archive-url=https://web.archive.org/web/20221128182944/https://news.stanford.edu/pr/01/elephants37.html |access-date=2023-03-23|archive-date=2022-11-28 }}</ref>

Comparison of hearing sensitivity through bone conduction and directly through the ear canal can aid audiologists in identifying pathologies of the [[middle ear]]—the area between the [[Eardrum|tympanic membrane]] (ear drum) and the cochlea (inner ear).    If hearing is markedly better through bone conduction than through the ear canal (air-bone gap),<ref>{{Cite book|title=A supplementary dictionary of audiology|last=Maltby, Maryanne Tate.|date=2012|publisher=Oxford University Press|isbn=978-0-19-965146-7|edition=1st|location=[Oxford]|oclc=822262757}}</ref> problems with the ear canal (e.g. ear wax accumulation), the tympanic membrane or [[ossicles]] can be suspected.<ref>{{Cite web|url=https://www.asha.org/public/hearing/Conductive-Hearing-Loss/|title=Conductive Hearing Loss|website=American Speech-Language-Hearing Association|language=en|access-date=2019-06-29}}</ref> This method was first discovered by Italian physician [[Hieronymus Capivacci]].<ref name = "Hearing Health Matters 2012-03-26">{{Cite web |date=2012-03-26 |title=Origins of Bone Conduction Hearing |url=https://hearinghealthmatters.org/waynesworld/2012/the-origins-of-bone-conduction-hearing/ |access-date=2022-03-02 |website=Wayne's World |language=en-US}}</ref>

==Hearing aids and implants==
[[File:Vintage Acousticon Hearing Aid By Dictograph Products Company, Bone Conduction, Made in the USA, Circa 1934 (12486155455).jpg|thumb|Image of a Vintage Acousticon Hearing Aid By Dictograph Products Company, Made in the US, Circa 1934.]]

=== History ===
The first bone conduction [[hearing aid]]s were invented in the 15th century. Italian physician [[Gerolamo Cardano|Girolamo Cardano]] realized that when a rod was placed between someone's teeth and attached the other end to a musical instrument, the person could hear the music despite their [[hearing loss]].<ref name = "Karger 2011">{{Cite journal |last1=Mudry |first1=Albert |last2=Tjellström |first2=Anders |date=2011 |title=Historical Background of Bone Conduction Hearing Devices and Bone Conduction Hearing Aids |url=https://www.karger.com/Article/FullText/323569 |journal=Implantable Bone Conduction Hearing Aids |series=Advances in Oto-Rhino-Laryngology |language=english |volume=71 |pages=1–9 |doi=10.1159/000323569 |pmid=21389699|isbn=978-3-8055-9700-5 |url-access=subscription }}</ref> This method was used by [[Ludwig van Beethoven|Beethoven]], as his hearing deteriorated towards the end of his life.<ref>{{Cite web |date=2021-05-26 |title=How a deaf Beethoven discovered bone conduction by attaching a rod to his piano and clenching it in his teeth |url=https://www.zmescience.com/science/how-a-deaf-beethoven-discovered-bone-conduction-by-attaching-a-rod-to-his-piano-and-clenching-it-in-his-teeth/ |access-date=2022-03-02 |website=ZME Science |language=en-US}}</ref> In the 1820s, French physician [[Jean Marc Gaspard Itard]] improved on this device by attaching the other end of the rod not to a musical instrument but to the mouth of another speaker. This invention was known as the Rod of Itard.<ref name="Hearing Health Matters 2012-03-26" /> In 1923, [[Hugo Gernsback]] created a new kind of bone conduction hearing aid called the "Osophone",<ref>{{cite patent|inventor-last=Gernsback|inventor-first=Hugo|inventor-link=Hugo Gernsback|publication-date=19 May 1923|issue-date=30 December 1924|title=Acoustic Apparatus|country-code=US|patent-number=1521287}}</ref> which he later elaborated on with his "Phonosone".<ref>{{cite journal|last1=Kennedy|first1=T. R. Jr.|year=1958|title=From Coherer to Spacistor|journal=Radio-Electronics|publisher=Gernsback Publications|volume=29|issue=4|pages=45–59|url=http://www.swtpc.com/mholley/RadioElectronics/Apr1958/Coherer_to_Spacistor.pdf|access-date=2010-06-01|archive-url=https://web.archive.org/web/20160527005605/http://www.swtpc.com/mholley/RadioElectronics/Apr1958/Coherer_to_Spacistor.pdf|archive-date=2016-05-27}}</ref> Bone conduction hearing aids have also been fitted to glasses, which fit tightly to the side of the head.<ref name="Spectacle Hearing Systems 2022-03-02">{{Cite web |title=Bone Conduction Glasses - Spectacle Hearing Aids |url=https://www.spectaclehearingsystems.co.uk/boneconduction.html |access-date=2022-03-02 |website=www.spectaclehearingsystems.co.uk}}</ref>

In the 1970s, a team of doctors in [[Gothenburg]], most notably Anders Tjellström, had the idea to implant a bone vibrator plate into the [[Mastoid part of the temporal bone|mastoid bone]] with an adjoining screw that allowed an external audio processor to be attached to conduct sound. The first three patients were implanted in 1977. The device gave good results and became known as a [[bone-anchored hearing aid]], or BAHA.<ref name="Karger 2011" /> In 2012, this idea was taken a step further by the introduction of the BONEBRIDGE device. Whereas a BAHA implant is a percutaneous device that requires the screw abutment to protrude through the skin, the BONEBRIDGE is a transcutaneous device and is fully implanted under the skin. In this case, the audio processor is held in place by magnets.<ref>{{Cite journal |title= Percutaneous Versus Transcutaneous Bone Conduction Implant System|url=https://www.researchgate.net/publication/23233979 |journal=  Otology & Neurotology|year=2008 |language=en |doi=10.1097/MAO.0b013e31816fdc90|pmid=18769364 |last1=Håkansson |first1=B. |last2=Eeg-Olofsson |first2=M. |last3=Reinfeldt |first3=S. |last4=Stenfelt |first4=S. |last5=Granström |first5=G. |volume=29 |issue=8 |pages=1132–1139 |s2cid=12593723 }}</ref>

=== Candidacy ===
Bone conduction devices are suitable for patients with [[Conductive hearing loss|conductive]] or [[mixed hearing loss]], with a functioning [[cochlea]] but problems with the [[Outer ear|outer]] or [[inner ear]] that prevent sound vibrations from reaching the cochlea.<ref name = "Hearinglink 2022-03-02">{{Cite web |title=Bone conduction hearing devices |url=https://www.hearinglink.org/your-hearing/implants/bone-conduction-hearing-devices/ |access-date=2022-03-02 |website=Hearing Link |language=en-GB}}</ref> This can be caused by conditions such as [[atresia]], [[microtia]], [[Goldenhar syndrome]] or [[Treacher Collins syndrome|Treacher Collins]].<ref>{{Cite web |title=Bone conduction hearing devices {{!}} Hearing implants |url=https://www.ndcs.org.uk/information-and-support/childhood-deafness/hearing-implants/bone-conduction-hearing-devices/ |access-date=2022-03-02 |website=www.ndcs.org.uk |language=en}}</ref> Bone conduction is also a good option for someone who cannot use traditional air conduction hearing aids.<ref name="Hearinglink 2022-03-02" />

Bone conduction devices are also used to help people with [[Unilateral hearing loss|single-sided deafness]], who have a non-functioning inner ear on one side. In this situation, the device picks up sounds on the non-functioning side and sends them as vibrations through the bone to the functioning cochlea on the other side.<ref name = "Ellsperman, Susan E. 2021-05-18">{{Cite journal |last1=Ellsperman |first1=Susan E. |last2=Nairn |first2=Emily M. |last3=Stucken |first3=Emily Z. |date=2021-05-18 |title=Review of Bone Conduction Hearing Devices |journal=Audiology Research |volume=11 |issue=2 |pages=207–219 |doi=10.3390/audiolres11020019 |issn=2039-4330 |pmc=8161441 |pmid=34069846|doi-access=free }}</ref>

=== Technology ===
There are many different types of bone conduction hearing aids but most of them work on the same principle and comprise necessary components like [[microphone]]s, [[signal processing]], [[energy supply]] and a [[transducer]] that generates vibrations. The microphone of the hearing aid picks up sound signals from the environment. The signal is then optimized and transmitted to the transducer, which generates vibrations. Depending on the specific bone conduction hearing aid system, the vibrations are either sent directly through the skull bone, or through the skin towards the inner ear. Finally, the inner ear picks up the vibrations and sends them to the [[auditory cortex]] in the brain.

Different bone conduction devices contain different features. Here are the key ones.

===Surgical and non-surgical bone conduction devices===
Surgical bone conduction devices consist of an internal implant and an external audio processor used to transmit sound.  They require surgery in order to implant the device, which is usually done as an outpatient procedure under [[General anaesthetic|general anesthetic]],<ref>{{Cite web |title=Bone Conduction Hearing Aids |url=https://www.dukehealth.org/treatments/ear-nose-and-throat/bone-conduction-hearing-aid |access-date=2022-03-02 |website=Duke Health |language=en}}</ref> however this depends on the device being implanted and the health condition of the patient.

Non-surgical devices only consist of the external audio processor. The processor simply vibrates, making both the skin and the bone vibrate, conducting the vibrations through to the [[cochlea]]. Non-surgical devices are ideal for children, who may not be old enough for implantation surgery or who have temporary conductive hearing loss caused by [[Otitis media|glue ear]] or [[Otitis|ear infections]].<ref>{{Cite web |title=Devices worn on a headband {{!}} Bone conduction hearing devices |url=https://www.ndcs.org.uk/information-and-support/childhood-deafness/hearing-implants/bone-conduction-hearing-devices/devices-worn-on-a-headband/ |access-date=2022-03-02 |website=www.ndcs.org.uk |language=en}}</ref>

There are various ways to attach non-surgical bone conduction devices to the skin, including [[headband]]s, [[adhesive]]s<ref>{{Cite web |title=Everything You Need To Know About BAHA Implants for Children {{!}} CCHAT Sacramento |url=https://www.cchatsacramento.org/blog-and-events/everything-you-need-to-know-about-baha-implants-for-children |access-date=2022-03-02 |website=www.cchatsacramento.org |language=en}}</ref> and bone conduction glasses.<ref name="Spectacle Hearing Systems 2022-03-02" /> Devices include the ADHEAR from [[MED-EL]],<ref>{{Cite web |title=ADHEAR {{!}} Savannah, GA |url=https://ahassavannah.com/adhear |access-date=2022-03-02 |website=ahassavannah.com}}</ref> the BAHA Start from [[Cochlear Limited|Cochlear]],<ref>{{Cite web |title=What is Baha Start - Southern ENT - News - A Better Africa |url=https://a-better-africa.com/show/southern-ent/post/1700 |access-date=2022-03-02 |website=a-better-africa.com}}</ref> BHM's contact mini or contact forte<ref>{{Cite web |title=contact mini - Pediatric bone conduction hearing aid by BHM-Tech Produktionsgesellschaft {{!}} MedicalExpo |url=https://www.medicalexpo.com/prod/bhm-tech-produktionsgesellschaft/product-128537-960400.html |access-date=2022-03-02 |website=www.medicalexpo.com |language=en}}</ref> and the Ponto Softband from [[Oticon|Oticon Medical]].<ref>{{Cite web |title=The New Ponto Softband from Oticon Medical Supports Early Access to Sound |url=https://www.audiologyonline.com/releases/new-ponto-softband-from-oticon-19633 |access-date=2022-03-02 |website=AudiologyOnline |language=en}}</ref> Unlike headbands or glasses-based devices, adhesive devices do not need to apply pressure against the head in order to transmit the vibration. Because of this, users of adhesive devices report wearing their device for longer each day.<ref>{{Cite journal |last1=Dahm |first1=Valerie |last2=Auinger |first2=Alice B. |last3=Liepins |first3=Rudolfs |last4=Baumgartner |first4=Wolf-Dieter |last5=Riss |first5=Dominik |last6=Arnoldner |first6=Christoph |date=June 2019 |title=A Randomized Cross-over Trial Comparing a Pressure-free, Adhesive to a Conventional Bone Conduction Hearing Device |url=https://journals.lww.com/otology-neurotology/Abstract/2019/06000/A_Randomized_Cross_over_Trial_Comparing_a.3.aspx |journal=Otology & Neurotology |language=en-US |volume=40 |issue=5 |pages=571–577 |doi=10.1097/MAO.0000000000002184 |pmid=31083074 |issn=1531-7129|url-access=subscription }}</ref>

===Surgical devices: percutaneous and transcutaneous devices===
A transcutaneous bone conduction device transmits sound signals, either electronic or mechanical, through the skin. In other words, there is closed, intact skin between the external audio processor and the internal implant. The processor is held in place over the implant using [[Magnetism|magnetic attraction]]. Transcutaneous devices currently on the market include the BAHA Attract,<ref>{{Cite web |title=Baha Attract |url=https://ais.southampton.ac.uk/baha-attract/ |access-date=2022-03-02 |website=University of Southampton Auditory Implant Service}}</ref> and Osia<ref>{{Cite press release |title=FDA clears Cochlear's innovative new Osia 2 hearing implant system |url=https://www.prnewswire.com/news-releases/fda-clears-cochlears-innovative-new-osia-2-hearing-implant-system-300970910.html |language=en |access-date=2022-03-02 |archive-url=https://web.archive.org/web/20241119204201/https://www.prnewswire.com/news-releases/fda-clears-cochlears-innovative-new-osia-2-hearing-implant-system-300970910.html |archive-date=2024-11-19 |website=www.prnewswire.com}}</ref> from Cochlear and the BONEBRIDGE from MED-EL.<ref name="Ears and Hearing UK 2022-03-02">{{Cite web |title=Bonebridge, Medel |url=https://earsandhearinguk.com/ear/deafness/treatments-surgical/implants/bone-conduction-devices/hearing-implants-bonebridge/ |url-status=live |archive-url=https://web.archive.org/web/20241119204320/https://earsandhearinguk.com/ear/deafness/treatments-surgical/implants/bone-conduction-devices/hearing-implants-bonebridge/ |archive-date=2024-11-19 |access-date=2022-03-02 |website=Ears & Hearing UK |language=en-GB}}</ref>
With a percutaneous device, part of the implant (known as the abutment) protrudes through the skin. The audio processor then snaps onto the abutment, providing a direct connection to the implant.<ref>{{Cite journal |last1=Håkansson |first1=B. |last2=Tjellström |first2=A. |last3=Carlsson |first3=P. |date=April 1990 |title=Percutaneous vs. transcutaneous transducers for hearing by direct bone conduction |journal=Otolaryngology–Head and Neck Surgery|volume=102 |issue=4 |pages=339–344 |doi=10.1177/019459989010200407 |issn=0194-5998 |pmid=2113260|s2cid=25857058 }}</ref> Percutaneous devices include the BAHA Connect from Cochlear<ref>{{cite web | title=Bone Conduction Hearing Aids |publisher=Johns Hopkins Medicine | date=15 December 2022 | url=https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/baha--the-implantable-hearing-device | archive-url=https://web.archive.org/web/20230418165657/https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/baha--the-implantable-hearing-device | archive-date=18 April 2023 | url-status=live}}</ref> and the Ponto from Oticon Medical.<ref>{{Cite web |title=The Oticon Ponto System|url=https://berkshearing.com/oticon-ponto-system |access-date=2022-03-02 |website=berkshearing.com}}</ref>
Percutaneous devices have been associated with skin complications, ranging from slight redness to the formation of [[granulation tissue]] and recurring infection. The most serious complications might require further surgery or abutment removal and subsequent reimplantation.<ref>{{Cite web |title=Percutaneous Versus Transcutaneous Bone Conduction Implant System: A Feasibility Study on a Cadaver Head |url=https://www.researchgate.net/publication/23233979 |access-date=2022-03-02 |website=ResearchGate |language=en}}</ref> One study into skin problems with percutaneous implants revealed a complication rate of up to 84%.<ref>{{Cite journal |last1=Mohamad |first1=Shwan |last2=Khan |first2=Imran |last3=Hey |first3=S. Y. |last4=Hussain |first4=S. S. Musheer |date=March 2016 |title=A systematic review on skin complications of bone-anchored hearing aids in relation to surgical techniques |journal=European Archives of Oto-rhino-laryngology|volume=273 |issue=3 |pages=559–565 |doi=10.1007/s00405-014-3436-1 |issn=1434-4726 |pmid=25503356|s2cid=10886157 }}</ref> In another study a meta-analysis of complications with osseointegrated hearing aids showed that revision surgery is required in up to 34.5% of cases.<ref>{{Cite journal |last1=Kiringoda |first1=Ruwan |last2=Lustig |first2=Lawrence R. |date=July 2013 |title=A meta-analysis of the complications associated with osseointegrated hearing aids |journal=Otology & Neurotology|volume=34 |issue=5 |pages=790–794 |doi=10.1097/MAO.0b013e318291c651 |issn=1537-4505 |pmid=23739555|s2cid=10274270 }}</ref> Transcutaneous devices were later designed to avoid or reduce recurring skin complications.<ref name="Ellsperman, Susan E. 2021-05-18" />

===Surgical devices: active and passive===
An active bone conduction device is one where the implant generates the vibrations that directly stimulate the bone. With a passive bone conduction device, the vibrations are generated by the audio processor before being passed through the skin or an abutment to reach the implant and the bone.<ref name = "NDCS 2022-03-02">{{Cite web |title=Different types of surgical implant {{!}} Bone conduction hearing devices |url=https://www.ndcs.org.uk/information-and-support/childhood-deafness/hearing-implants/bone-conduction-hearing-devices/different-types-of-surgical-implant/ |access-date=2022-03-02 |website=www.ndcs.org.uk |language=en}}</ref> The main active bone conduction devices available are the BONEBRIDGE from MED-EL<ref name="Ears and Hearing UK 2022-03-02" /> and the Osia from Cochlear.<ref>{{Cite press release |last=Limited |first=Cochlear |title=FDA clears Cochlear's innovative new Osia® 2 hearing implant system |url=https://www.prnewswire.com/news-releases/fda-clears-cochlears-innovative-new-osia-2-hearing-implant-system-300970910.html |access-date=2022-03-02 |website=www.prnewswire.com |language=en}}</ref> Both are active transcutaneous devices. The external audio processor picks up sound vibrations and transmits them electronically through the skin to the internal implant, which directly and actively vibrates the bone. These vibrations are conducted through the skull bone to the cochlea and are processed as normal.<ref name="NDCS 2022-03-02" />

The main passive bone conduction devices are the BAHA Attract<ref>{{Cite web |title=Baha® Attract |url=https://ais.southampton.ac.uk/baha-attract/ |access-date=2022-03-02 |website=Auditory Implant Service |language=en-GB}}</ref> and BAHA Connect<ref>{{Cite web |title=Baha – The Implantable Hearing Device |url=https://www.hopkinsmedicine.org/otolaryngology/specialty_areas/hearing/hearing-aids/baha.html |access-date=2022-03-02 |website=www.hopkinsmedicine.org |language=en}}</ref> from Cochlear, the Ponto from Oticon<ref>{{Cite web |title=The Oticon Ponto System {{!}} A Complete Hearing Solution |url=https://berkshearing.com/oticon-ponto-system |access-date=2022-03-02 |website=berkshearing.com}}</ref> and the Alpha 2 MPO from [[Medtronic]].<ref>{{Cite web |title=Sophono Medtronic Alpha 2 MPO Processor |url=https://getremed.gr/προϊόντα/medical-products-en/office-equipment/audiology-equipment/audiological/sofono-alpha2/?lang=en |access-date=2022-03-02 |website=Getremed |language=en-US}}</ref> The BAHA Connect and Ponto are passive percutaneous devices, whereby the audio processor is fixed onto an abutment placed through the skin. The audio processor vibrates, sending the vibrations via the abutment to the implant and then through the bone to the cochlea.<ref name="NDCS 2022-03-02" /> The BAHA Attract and Alpha 2 are transcutaneous devices but they work in a similar way. The audio processor vibrates, sending mechanical vibrations to the implant through the bone. However, unlike with the percutaneous devices, the vibrations from the audio processor pass through the skin before they reach the internal implant. These vibrations are then conducted through the skull bones to the cochlea and are processed as normal, just like with an active device.<ref name="NDCS 2022-03-02" />

Active transcutaneous and passive percutaneous bone conduction devices tend to deliver better sound quality than passive transcutaneous ones. Passive transcutaneous devices send sound vibrations through the skin, and as they pass through the skin, they lose some of their strength, causing [[signal attenuation]] of up to 20[[Decibel|dB]].<ref name="Ellsperman, Susan E. 2021-05-18" /> To counteract this, passive transcutaneous devices may require the use of strong magnets that squeeze the skin to achieve optimal conduction. This can lead to pain and irritation of the skin and [[soft tissue]] between the two magnets, and in worst cases cause [[necrosis]].<ref name="Ellsperman, Susan E. 2021-05-18" /> A study found that major complications—defined as complications requiring active management, such as post-operative [[seroma]], [[hematoma]], wound infections, skin [[ulcer]]ations, and [[Wound dehiscence|dehiscence]]—were found in 5.2% of cases.<ref>{{Cite journal |last1=Cooper |first1=Timothy |last2=McDonald |first2=Brendan |last3=Ho |first3=Allan |date=October 2017 |title=Passive Transcutaneous Bone Conduction Hearing Implants: A Systematic Review |journal=Otology & Neurotology|volume=38 |issue=9 |pages=1225–1232 |doi=10.1097/MAO.0000000000001518 |issn=1537-4505 |pmid=28719403}}</ref>

===Device overview===
{| class="wikitable"
!Device
!Surgical 
!Non-surgical 
!Active<br>surgical 
!Passive<br>surgical 
!Transcutaneous<br>surgical 
!Percutaneous<br>surgical 
|-
!ADHEAR

|x 
|✓ 
|N/A 
|N/A 
|N/A 
|N/A 
|-
!Alpha 2

|✓ 
|x 
|x 
|✓ 
|✓ * (see above) 
|
|-
!BAHA Attract 
|✓ 
|x 
|x 
|✓ 
|✓ * (see above) 
|x

|-
!BAHA Connect 
|✓ 
|x 
|x 
|✓ 
|x
|✓ 
|-
!BAHA Start

|x 
|✓ 
|N/A 
|N/A 
|N/A 
|N/A 
|-
!BONEBRIDGE

|✓ 
|x 
|✓ 
|x 
|✓ 
|x 
|-
!Osia

|✓ 
|x 
|✓ 
|x 
|✓ 
|x 
|-
!Ponto

|✓ 
|x 
|x 
|✓ 
|x 
|✓ 
|}

==Products==
[[File:Goldendance_bone_conduction_headset.jpg|thumb|A bone conduction [[Audio headset|headset]] (''GoldenDance'' brand)]]

Bone conduction products are usually categorized into three groups:

* Ordinary products, such as [[hands-free]] headsets or [[headphones]]
* [[Bone-anchored hearing aid]]s and [[assistive listening devices]]
* Specialized communication products (e.g. for underwater or high-noise environments)

One example of a specialized communication product is a bone conduction speaker that is used by [[Scuba diving|scuba divers]]. The device is a rubber over-moulded, [[Piezoelectricity|piezoelectric]] flexing disc that is approximately {{convert|40|mm|in}} across and {{convert|6|mm|in}} thick. A connecting cable is molded into the disc, resulting in a tough, waterproof assembly. In use, the speaker is strapped against one of the dome-shaped bone protrusions behind the ear and the sound, which can be surprisingly clear and crisp, seems to come from inside the user's head.<ref>{{cite web|last1=Banks|first1=Lindsey|title=The History of Bone Conduction|url=http://juliawall.sites.gettysburg.edu/westpoint61/the-history-of-bone-conduction/users/765|website=gettysburg.edu|access-date=11 July 2015|archive-url=https://web.archive.org/web/20180715040318/http://juliawall.sites.gettysburg.edu/westpoint61/the-history-of-bone-conduction/users/765|archive-date=15 July 2018}}</ref>

== Notable uses ==
The [[Google Glass]] device employs bone conduction technology for the relay of information to the user through a [[transducer]] that sits beside the user's ear. The use of bone conduction means that any vocal content that is received by the Glass user is nearly inaudible to outsiders.<ref>{{cite news|title=Google Glass – hands-on review|url=https://www.theguardian.com/technology/2013/jul/02/google-glass-review-augmented-reality|access-date=3 July 2013|newspaper=The Guardian|date=2 July 2013|author=Charles Arthur}}</ref>

German broadcaster Sky Deutschland and advertising agency BBDO Germany collaborated on an advertising campaign that uses bone conduction that was premiered in [[Cannes|Cannes, France]], at the International Festival of Creativity in June 2013. The "Talking Window" advertising concept uses bone conduction to transmit advertising to public transport passengers who lean their heads against train glass windows. Academics from Australia's Macquarie University suggested that, apart from not touching the window, passengers would need to use a dampening device that is made of material that would not transmit the vibration from the window in order to not hear the sound.<ref>{{cite news|title=Bone conduction: the new front in guerilla advertising|url=http://theconversation.com/bone-conduction-the-new-front-in-guerilla-advertising-15984|access-date=15 July 2013|newspaper=The Conversation Australia|date=12 July 2013|author=Catherine McMahon|author2=Phillip Nakad}}</ref><ref>{{cite news|title=Talking train window adverts tested by Sky Deutschland|url=https://www.bbc.co.uk/news/technology-23167112|access-date=15 July 2013|newspaper=BBC News|date=3 July 2013|author=Leo Kelion}}</ref>

[[Land Rover BAR]] employed 'military' bone conduction technology, designed by [[BAE Systems]],  within their helmets for use within the [[2017 America's Cup]].<ref>{{Cite web|url=http://land-rover-bar.americascup.com/en/news/258_The-challenge-of-onboard-communication.html|title=The challenge of onboard communication - Land Rover Ben Ainslie Racing|last=Racing|first=Ben Ainslie|website=land-rover-bar.americascup.com|language=en|access-date=2018-01-12|archive-url=https://web.archive.org/web/20170905235510/http://land-rover-bar.americascup.com/en/news/258_The-challenge-of-onboard-communication.html|archive-date=2017-09-05}}</ref> The helmets allowed the crews to communicate effectively with each other under race conditions and within the harsh, noisy environment; whilst maintaining situational awareness due to their ears being uncovered.<ref>{{Cite web|url=https://www.baesystems.com/en/article/our-bone-conduction-technology-is-set-to-raise-the-bar-in-bermuda|title=Our bone conduction technology is set to raise the bar in Bermuda {{!}} BAE Systems {{!}} International|website=BAE Systems {{!}} International|language=en|access-date=2018-01-12}}</ref>

In March 2019 at [[National Maritime Museum|The National Maritime Museum]], London, British composer [[Hollie Harding]] premiered the use of Bone Conduction Headphones as part of a musical performance.<ref>{{Cite web|url=https://www.rmg.co.uk/whats-on/concert-melting-shifting-liquid-world|title=Concert: Melting, Shifting, Liquid World|date=2019-01-29|website=Royal Museums Greenwich {{!}} UNESCO World Heritage Site In London|language=en|access-date=2019-03-21}}</ref> The use of the technology allowed the audience to listen to a pre-recorded musical track on the headsets, whilst a live orchestra performed a separate but related musical track. This multilayered effect meant that electronic and digitally-edited sounds could be heard in conjunction with live music without the use of loud-speakers for the first time and that the source of sounds could appear to be close to, far from, or all around the listener.

Research has found that the use of bone conduction headphones can help people distinguish between their own voice and the voice of others.<ref name = "Psypost 2023-04-08">{{Cite web |last=Dolan |first=Eric W. |date=2023-04-08 |title=Your own voice "is not just a sound": Bone-conduction tech offers new insights into voice perception |url=https://www.psypost.org/2023/04/your-own-voice-is-not-just-a-sound-bone-conduction-tech-offers-new-insights-into-voice-perception-74872 |access-date=2023-04-12 |website=PsyPost |language=en-US}}</ref> The findings have potential clinical relevance for conditions such as schizophrenia.<ref name = "Psypost 2023-04-08" />

== Safety ==
Because bone conduction headphones transmit sound to the inner ear through the bones of the skull, leaving the ears free to pick up sound from the environment, users can listen to audio while maintaining greater situational awareness than with acoustic in- or over-ear headphones. However, users may still be less aware of their environment than if not using headphones.<ref>{{cite journal |author=May, Kennan R.; Walker, Bruce N. |date=May 2017 |title=The effects of distractor sounds presented through bone conduction headphones on the localization of critical environmental sounds |journal=Applied Ergonomics |volume=61 |pages=144–158 |doi=10.1016/j.apergo.2017.01.009 |pmid=28237013 }}</ref>

== See also ==
* [[Bone conduction auditory brainstem response]]
* [[Cochlear Baha]]
* [[Headphones]]
* [[Rinne test]]
* [[SoundBite Hearing System]]
* [[Weber test]]

==References==
{{Reflist}}

{{Physiology of hearing and balance}}

{{DEFAULTSORT:Bone Conduction}}
[[Category:Assistive technology]]
[[Category:Auditory system]]
[[Category:Otology]]