AN IMPLANT that will allow deaf people to hear music clearly is on its way. The cochlear implant being developed by the National Physical Laboratory (NPL) in Teddington, UK, will enable deaf people to hear sounds over a wide range of frequencies.
Existing implants respond to a limited range of frequencies, concentrating on those prominent in the human voice. While they allow people to hear speech, they are not good for listening to music.
Conventional hearing aids, meanwhile, simply amplify sound rather than making it clearer. 鈥淭he typical deterioration in the sensory receptors of the inner ear results in distortion of sound, even when it comes from the most sophisticated hearing aids available,鈥� says Angela King, senior audiologist at the Royal National Institute for the Deaf in London.
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The prototype, developed by Markys Cain and colleagues at NPL in collaboration with the Institute of Nanotechnology in Stirling, UK, has four bar-shaped elements that vibrate in response to sound. Each is coated with a film of polyvinylidene fluoride, a piezoelectric material. By adjusting the length and diameter of the elements, the researchers have tuned each to resonate at a different, narrow range of frequencies.
When a sound, such as a musical note, causes one of the elements to vibrate, the flexing of the piezoelectric material produces a small voltage. This is transmitted directly to the auditory nerve in the cochlea. Unlike conventional implants, it does not require an external power supply.
The prototype is about 2 centimetres square at present, but the researchers have teamed up with the nanotechnology group at Cranfield University in Bedfordshire, UK, to create a version that will fit into the ear. 鈥淲e would need 10 resonating elements for speech and 20 or maybe more for music,鈥� says Bill Nimmo, a member of the NPL team. 鈥淭he challenge is to miniaturise the elements so that they still resonate at audible frequencies.鈥�
This means a commercial implant is likely to be at least 10 years away. But once complete, the hearing aid will give people manual control over the frequencies they hear, enabling them to tune in to individuals in a crowded room and filter out the background chatter.
