AUDITORY FILTER SHAPES IN NORMAL-HEARING, NOISE-MASKED NORMAL, AND ELDERLY LISTENERS

To dissociate the effects of age and hearing impairment on changes in frequency selectivity, auditory filter shapes were measured at 2 kHz i n four groups of subjects: ( 1) normal-hearing young subjects; (2) nor mal-hearing elderly subjects; (3) elderly hearing-impaired listeners; and (4) young normal-hearing listeners with simulated hearing losses. Filter shapes were derived using a modified version of the notched-noi se procedure [Glasberg and Moore, Hear, Res. 47, 103-138 (1990)]. Equi valent rectangular bandwidths (ERBs) of auditory filters were not sign ificantly different in young and elderly subjects with normal 2-kHz he aring. Furthermore, filter widths for young subjects with 20- and 40-d B simulated hearing losses overlapped with those obtained from elderly subjects with corresponding degrees of actual hearing loss. One measu re that did show significant differences between actual and simulated hearing losses was the degree of filter asymmetry; auditory filters in hearing-impaired listeners were more asymmetrical than those obtained from noise-masked normal-hearing subjects. The dynamic range of audit ory filters, however, was comparable for hearing-impaired and noise-ma sked listeners. Lastly, post-filter detection efficiency was also simi lar for young and elderly subjects with equivalent hearing levels. The se findings suggest that the reduced frequency selectivity often repor ted for older listeners can be attributed, primarily, to hearing loss rather than increased age. Implications of the results for speech perc eption in the elderly and models of