Bone Conduction Hearing Device Works Through Teeth

The system capitalizes on the natural acoustic benefit provided by the patient's own pinna (outer ear) to capture and direct sound via bone conduction to the inner ear, bypassing the external auditory canal and middle ear. The system is designed to deliver sound across a broad frequency range from 250 to more than 12,000 Hz.

The SoundBite hearing system detects sound using a miniature microphone placed in an open-fit dome within the ear canal of the impaired ear. The microphone is permanently attached by a slender transparent tube to a behind the ear (BTE) wireless transmitter unit. The BTE then uses a digital signal processor circuit and a second noise cancellation microphone to process the sound, using a wireless chip to transmit the signals to a discreet, removable, in the mouth (ITM) prosthetic hearing device, which in turn sends imperceptible vibrations via the teeth near-simultaneously to both cochleae.

The ITM device is custom made to fit around either the upper left or right molars, does not require any alteration of the teeth, and is easily inserted and removed by the user. It contains electronic components, a sealed, flat, rechargeable battery, a wireless receiver that picks up the transmissions from the BTE, and a small actuator that converts the signals into vibratory energy. All of the miniaturized components are hermetically sealed inside a dental grade acrylic. An inductive charger unit is provided to charge both the BTE microphone unit and ITM hearing device. The SoundBite hearing system is under development by Sonitus Medical (San Mateo, CA, USA), and is currently intended for investigational use alone.

Common bone-anchored hearing aids use a surgically implanted titanium abutment to transmit sound by direct conduction through bone, usually in the mastoid process. A sound processor on the exposed part of the abutment transmits sound vibrations to the external part of the titanium implant; the implant then vibrates the skull and inner ear, which stimulate the nerve fibers of the inner ear, allowing hearing. The hearing aid can be used once osseointegration of the implant is complete, usually two to six months after surgery.

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