Bone Conduction

Bone conduction is the conduction of sound to the inner ear through the bones of the skull.

Bone conduction is the reason why a person's voice sounds different to him/her 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. This also explains why a recording of one's own voice sounds higher than one is accustomed to.

Some hearing aids employ bone conduction, achieving an effect equivalent to hearing directly by means of the ears. A headset is ergonomically positioned on the temple and cheek and the electromechanical transducer, which converts electric signals into mechanical vibrations, sends sound to the internal ear through the cranial bones. Likewise, a microphone can be used to record spoken sounds via bone conduction. The first description, in 1923, of a bone conduction hearing aid was Hugo Gernsback's "Osophone", which he later elaborated on with his "Phonosone".

Bone conduction products are usually categorized into three groups

  • Ordinary products such as hands-free headsets or headphones
  • Hearing aids and assistive listening devices
  • Specialized communication products (e.g. underwater & high-noise environments)

Bone conduction products have following advantages over traditional headphones:

  • Maintains sound clarity in very noisy environments, can be used with hearing protection

There are some disadvantages:

  • Crosstalk between stereo channels. The effect is insignificant for spatial localization of sound sources.
  • Some implementations require more power than headphones
  • Reduced frequency bandwidth

One example of a bone conduction speaker is a rubber over-moulded piezo-electric flexing disc about 40mm across and 6mm thick used by scuba divers. The connecting cable is moulded into the disc, resulting in a tough, water-proof assembly. In use the speaker is strapped against one of the dome-shaped bone protrusions behind the ear. As would be expected, the sound produced seems to come from inside the user's head, but can be surprisingly clear and crisp.

Bone conduction transmission can be used with individuals with normal or impaired hearing. There are several products on the market that exploit the bone conduction transmission pathway for sound. Some of these include the AquaFM and the SwiMP3 which are devices for transmitting sound to swimmers.

Other articles related to "conduction, bone conduction, bone":

Rinne Test - Air Vs. Bone Conductive Hearing Loss
... Air conduction uses the apparatus of the ear (pinna, eardrum and ossicles) to amplify and direct the sound whereas bone conduction bypasses some or all ... Positive/negative In a normal ear, air conduction (AC) is better than bone conduction (BC) AC > BC this is called a positive Rinne In conductive hearing ... In this case, that parameter is if air conduction (AC) is better than bone conduction (BC) ...
Cochlear Limited - Products
... These include cochlear implants, bone conduction implants, implants for electro-acoustic stimulation and implants for direct acoustic stimulation ... In 2005, Cochlear acquired the Swedish company Entific Medical Systems, renamed Bone Anchored Solutions (BAS) ... Through this acquisition, Cochlear expanded its "hearing solutions portfolio" to include the Baha bone conduction implant for conductive hearing loss, mixed hearing loss and ...
Weber Test - Considerations and Limitations
... Weber test considerations The Weber test reflects conduction loss in the ipsilateral ear because, in the event of impaired conduction, ipsilateral sensorineural hearing is perceived as louder ... ear has a positive Rinne test (AC>BC), that generally means the absence of conduction loss in that ear, and the reason sound had been perceived as louder on that side is because a sensorineural ... used in cases of unilateral hearing loss and establishes which ear has the greater bone conduction ...
Pure Tone Audiometry - Cross Hearing and Interaural Attenuation
... cochlea can also be stimulated to varying degrees, via vibrations through the bone of the skull ... Air conduction results in isolation, give little information regarding the type of hearing loss ... When the thresholds obtained via air conduction are examined alongside those achieved with bone conduction, the configuration of the hearing loss can be determined ...

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