Tooth-mounted hearing aid offers hope for deaf

Beethoven used a primative version of a new tooth-mounted hearing device offering hope for deaf people, New Scientist’s Linda Geddes reports.


Beethoven is said to have overcome his deafness by attaching a rod to his piano and clenching it between his teeth, enabling the musical vibrations to travel through his jawbone to his inner ear.

Next year, a similar but less unwieldy approach might restore hearing to people with a common form of deafness.

Single-sided deafness (SSD) affects around 9 million people in the US, and makes it difficult for them to pinpoint the exact source of sounds. This can make crossing roads extremely hazardous, and also makes it hard to hear conversations in noisy rooms.

Sonitus Medical of San Mateo in California has created a small device that wraps around the teeth.

It picks up the sounds detected from a tiny microphone in the deaf ear and transforms them into vibrations.

These then travel through the teeth and down the jawbone to the cochlea in the working ear, where they are transmitted to the brain providing stereo sound.

The same process of “bone conduction” explains how we hear our own voices, and why they sound different when they are recorded and played back to us.

Some existing hearing aids also use bone conduction to transmit sounds to the cochlea, but these either require a titanium post to be drilled into the skull, or rely on cumbersome headsets.

It also differs from conventional hearing aids, which employ air conduction to simply turn up the volume of sound travelling into the ear. The Cleveland Clinic in Ohio voted Sonitus’s device its top medical innovation for 2010.

Sonitus is testing the device in people with SSD. One study suggests the device is comfortable and doesn’t damage the teeth, and that it improved speech intelligibility in noisy surroundings.

The firm may start testing the device in people with other forms of deafness and at least one functioning cochlea.

The company plans to submit its results to the US Food and Drug Administration for approval in early 2010, and if all goes to plan, the device should become available later in the year. It will lend an ear to millions.

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