Critical‐band compression method of speech enhancement for elderly people: Investigation of syllable and word intelligibility

Abstract

Auditory filters for the hearing impaired tend to be wider than those of normal hearing people. Thus, the frequency selectivity decreases because of increased masking effects [Glasberg and Moore, J. Acoust. Soc. Am., 79(4), 1020‐1033, 1986]. We have developed a method, called compression, in which the critical band is compressed along the frequency axis [Yasu et al., Handbook of the International Hearing Aid Research Conference (IHCON), 55, Lake Tahoe, 2004]. We investigated whether our method improves syllable and word intelligibility. Thirty one elderly people participated in experiments. First, we measured the auditory filter bandwidth using a notched noise method [Patterson, J. Acoust. Soc. Am., 59(3), 640‐654, 1976]. Second, we conducted syllable and word intelligibility tests. The compression rates of critical‐band compression were set to 0% for the original, and 25%, 50%, and 75%. The results were that the percentages of correct responses were almost the same at 0%, 25% and 50% compression rates for syllable and word intelligibility. A significant correlation was not obtained between the compression rate of processing and the auditory filter bandwidth. [Work supported by JSPS.KAKENHI (16203041) and Sophia University Open Research Center from MEXT.]