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Improving Cochlear Implants
by Melissa Lee Phillips
Experiencing the limitations of his own cochlear implant inspired Chad Ruffin to better the device.
Cochlear implants have helped bring profoundly deaf individuals into the hearing world, but one HHMI fellow says the technology needs improvement. Chad Ruffin says users have a tough time understanding speech in noisy environments, largely because today's implants transmit almost no information about pitch—the tone that allows the hearer to distinguish one sound from another, as in picking one voice out of the din. Ruffin knows firsthand; he received an implant 6 years ago.
He hopes to correct the limitations of cochlear implants through his research. An HHMI medical research training fellow at the Virginia Merrill Bloedel Hearing Research Center at the University of Washington in Seattle, Ruffin is studying how cochlear implants can be programmed to transmit more information on frequency, thereby enabling the user to discriminate between the pitch of different voices.
Each implant contains a tiny computer that receives sound information from the environment and then uses speech-processing programs to relay this information—or at least some of it—to the brain. Current speech processors rely almost entirely on the intensity of sounds within a few frequency bands; that is, they are sensitive mainly to the changes in amplitude in a series of spoken syllables or words. Although this feature gives "good speech perception in the quiet," Ruffin says, "if you start to add complex sounds, such as music or noise, the perception goes down dramatically."
Photo: Brian Smale