Hearing Aid and Cochlear Implant Technologies Are Being Combined

Originally Published MDDI June 2004

R&D DIGEST

Erik Swain

Combining two technologies may produce a breakthrough enabling patients to hear better than with just one technology alone.

A team of three researchers has been applying advanced hearing-aid technologies to cochlear implants. They have found that the combination reduces background noise, improves speech understanding, and enhances sound quality.

The idea came to King Chung, an assistant professor of audiology at Purdue University (West Lafayette, IN), at a cochlear implant conference seven years ago. She recognized that some of the problems discussed about cochlear implants had been resolved in hearing aids. But only recently did she decide to act on it. “In recent years, we have observed great leaps in hearing-aid technologies,” she said. “I thought it was time to apply [them] to cochlear implants.” She enlisted Fan-Gang Zeng, a professor at the University of California at Irvine, and Susan Waltzman, a professor at the New York University School of Medicine, to help research development opportunities. They recently published their findings in Acoustic Research Letters Online.

Hearing aids are advanced in reducing ambient noise, and the newest versions are well designed for user comfort. Cochlear implants are advanced in electrode mechanics, processor miniaturization, and coding strategies. “Our study shows that by combining these two technologies, cochlear implant users can understand speech better and be more comfortable when they listen in background noise,” Chung said. “Cochlear implant users also prefer the conditions in which advanced hearing-aid technologies were applied as a preprocessor to their cochlear implants.”

One advanced hearing-aid feature is the incorporation of adaptive directional microphones that track the direction of background noise. These microphones reduce noise significantly even if it is moving in the environment. In the study, cochlear implant users who used directional microphones improved their speech understanding by 11.7%. 
Chung said that other hearing-aid technologies that may be useful in cochlear implants include auditory-scene-analysis and noise-reduction 
algorithms, and automatic switches that, for example, change to a different mode when the user is on the telephone.

The team is suggesting that product developers integrate hearing-aid algorithms and hardware into the software of cochlear implant speech processors. “At the moment, we are advocating that hearing-aid and cochlear implant manufacturers collaborate” on a project, Chang said. “If they collaborate, we think it'll probably take one to two years to realize [the results] in commercial products.”

Another avenue of development, she said, would be to add an in-the-ear hearing-aid unit to existing cochlear implants. 

The team is planning more research to find the most practical ways to combine the two technologies, whether certain discoveries are best implemented in hearing-aid or cochlear implant modules, and whether there are any negative interactions between the technologies. 
One follow-up study with adaptive directional microphones is being supported by a New Investigators Grant from the American Academy of Audiology. 

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