Irvine, Calif., Jan. 25, 2005 -- There's a reason why we listen to music on the FM dial of our radios – it just sounds better than it does on AM.
And this reason also holds true for cochlear implants and hearing aids. UC Irvine School of Medicine researchers have found that improving frequency modulation, or FM, reception on cochlear implants and hearing aids may increase the quality of life for the millions of Americans who use these devices.
Dr. Fan-Gang Zeng and his colleagues at UCI and the Peking Union Medical College Hospital in Beijing discovered that enhancing the detection of frequency modulation may significantly boost the performance of many hearing aids and automatic speech recognition devices by separating and blocking out background noise and increasing tonal recognition, which is essential to hearing music and certain spoken languages. Study results appear this week in the early online edition of Proceedings of the National Academy of Sciences.
Some 30 million Americans have some form of hearing loss, and some 4 million of these people benefit from using hearing aids or cochlear implants. But limitation on sound quality and overamplification of background sound can hinder their uses.
"Many hearing-aid – particularly cochlear-implant – users have trouble enjoying music or listening to conversation in a crowded room," said Zeng, research director of the Hearing and Speech Lab at UCI. "But we've found that FM modifications to both existing and future devices may overcome these difficulties."
Known as a leading expert in cochlear-implant research, Zeng and his colleagues looked into the reasons behind these limitations, specifically focusing on the two parameters of sound: amplitude (the height of a sound wave) and the frequency (the number of sound waves per unit of time).
Thirty-four normal-hearing and 18 cochlear-implant subjects participated in the study. They were tested on three speech-perception tasks known to be notoriously difficult for cochlear-implant users: speech recognition with a competing voice, speaker recognition and Mandarin-tone recognition. The researchers tested the amplitude modulation (AM) and FM from a number of frequency bands in speech sounds and tested the relative contributions to speech recognition in acoustic and electric hearing.
They found that AM works well in quiet environments but less well where background noise is present. In turn, FM enhances speech, tone and speaker recognition when other noise was present, and overall provided a better quality of tonal sound than AM does. Current cochlear implants extract only AM information, limiting significantly their performance under realistic listening situations.
These FM modifications, Zeng adds, can particularly assist Asians and Africans who speak tonal languages, such as Mandarin, in which tonal variations are vitally important. "As with your radio, music sounds better on the FM dial, and enhancing the FM reception on hearing devices can go a long way to helping people listen to and enjoy the beautiful music of their everyday lives in ways they've been unable to do," Zeng said.
Kaibo Nie, Ginger S. Stickney, Ying-Yee Kong, Michael Vongphoe and Ashish Bhargave of UCI and Chaogang Wei and Keli Cao of the Peking Union Medical College Hospital assisted with the study. The National Institutes of Health and the Chinese National Natural Science Foundation provided support.
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