My dad was like a little kid in a toy store. He would go around asking, ‘What’s that noise? Where is it coming from?’ He was exploring a whole new world of sound that had long been forgotten. So wrote Vernon Hise last October after his father, Bobby, had received an experimental implant designed to help him hear after years of total deafness.
This testimonial is for a new type of cochlear implant--a hearing aid, surgically implanted in the inner ear, designed to restore partial hearing to completely deaf people--invented by Blake Wilson, director of the Center for Auditory Prosthesis Research at the Research Triangle Institute in North Carolina. A cochlear implant consists of an external speech processor that converts sound to electric signals and then transmits them to several electrodes. In turn the electrodes directly stimulate auditory nerves in the ear. Although each electrode is tuned to a different frequency, the electric signals electrodes emit can interfere with one another, muffling the sound the patient hears. To improve the quality of sound, Wilson devised a method, called continuous interleaved sampling, that uses brief pulses, each delivered at a different time, rather than continuous signals. This way the pulses don’t have a chance to interfere with one another.
Soon after Wilson got the idea in 1989, he rigged up a demonstration. The first patient who tried it noticed an immediate improvement in performance, says Wilson. We then worked to improve it, and the patient again noticed a large difference. That suggested we should test the idea with many people. One of the biggest advantages of this approach is that it can be tailored to a person’s individual hearing deficiency.
Several foreign companies, including Med-El in Austria and Bionic Systems in Belgium, are already using a version of the processor in their cochlear implants. In this country, Advanced Bionics in Sylmar, California, recently received fda approval for an implant based on the technology. Wilson’s new challenge is to reduce the manufacturing costs so that the implants can be sold in China.
