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Commun Sci Disord. 2000;5(1): 1-15.
Acoustic Evaluation of Noise Reduction in a Hearing Aid
Yingyong Qi` , and Chul-Hee Choi`
Copyright ©2000 The Korean Academy of Speech-Language Pathology and Audiology
Yingyong Qi, 최철희(Chul-Hee Choi)
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The purpose of this study is to acoustically evaluate the noise reduction function of one specific type of hearing aid (Phonak, Piconet2 AZ). Recording were made using a microphone that was mounted on the Zwislocki coupler inside KEMAR. The signal- to- noise ratio (SNR) of the recorded signals were obtained for a variety of recording environments . These include: (1) high (0 dB SNR) and low (15 dB SNR) noise level, (2) three different types of noise (white, cafeteria, and multitalker ), and (3) three different hearing aid programs (Peak Clipping, Wide Dynamic Range Compression, and Super Compression with adaptive recovery Time). The SNRs were calculated using the signal- to- noise ratio estimation algorithm proposed by Qi et al. (in press ). In this algorithm, the signal was computed as the energy of correlated components of speech. Noise was computed as the energy of the remaining uncorrelated or random components of speech. The uncorrelated component was obtained by systematically removing any short- and long- term correlation exhibited by the original signal. The differences in SNR when the AudioZoom function was turned on or off was computed to evaluate the noise reduction function of the hearing aid. Results indicated that the SNR was about 1- 2 dB higher when AudioZoom was turned on than when it was turned off at the high noise level. This magnitude of the SNR increase depended on the type of noise presented in the environment. The SNR increase was significantly higher for white noise than for cafeteria noise or multitalker noise. No increase of SNR was observed when the AudioZoom function was turned on at the low noise level. The effect of hearing aid program is also not significant. It appears that the AudioZoom function is most effective when high- level white noise is present . It is not as useful when low- level, speech- like noise is present , no matter what hearing aid program is used.
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