Hearing Through Your Teeth

Most of us remember that Beethoven went deaf.  We often wonder how it is that such a one could compose fabulous works of music when it was impossible to hear what he was composing. As history tells us, Beethoven didn’t let a little thing like deafness stop him.

Beethoven devised a method by which he could hear what he was playing, what the music sounded like. He overcame his deafness by attaching a rod to his piano and clenching it between his teeth.  As he played, the vibrations traveled through the rod, through his teeth, through his jawbone, and into his inner ear. 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.

There are millions of people in the US and around the world who are deaf. Some of these people (about 9 million in the US) suffer from what is know as single-sided deafness (SSD), which makes it difficult 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.

In a modern take on Beethoven’s solution, Sonitus Medical of San Mateo in California has created a small devise 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 up the jawbone to the cochlea in the working ear, where they are transmitted to the brain providing stereo sound. (Pictures show the devise in the teeth and the accompanying BTE [behind-the-ear] module.)

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 traveling into the ear. The Cleveland Clinic in Ohio voted Sonitus’s device its top medical innovation for 2010.

The devise is currently being tested. One study suggests the devise is comfortable and doesn’t damage the teeth, and that it improved speech intelligibility in noisy surroundings. The firm may start testing the devise in people with other forms of deafness and at least one functioning cochlea.

The company planned to submit its results to the US Food and Drug Administration for approval early this year, and if all goes as planned, it should become available later in the year.

Source:  New Scientist December 2009 & January 2010