Auditory filter shapes in normal-hearing, noise-masked, and elderly subjects.

Abstract

Previous studies of frequency selectivity have suggested a strong positive correlation between age and the width of auditory filters [Patterson etal., J. Acoust. Soc. Am. 72, 1788–1803 (1982)]. However, given that absolute thresholds are generally higher in older listeners, it is unclear whether the broader filter shapes are a consequence of aging perse or are associated with changes in absolute sensitivity. To dissociate the effects of hearing loss and increased age on changes in frequency selectivity, this study measured auditory filter shapes at 2 kHz in (1) normal-hearing young subjects; (2) elderly (over age 65) subjects with normal 2-kHz thresholds; (3) young subjects with 2-kHz thresholds elevated either 20 or 40 dB by a narrow-band masker; and (4) elderly subjects with varying degrees of hearing loss at 2 kHz. Rounded exponential filter shapes were derived from the data using the method described by Patterson [J. Acoust. Soc. Am. 59, 640–654 (1976)]. Equivalent rectangular bandwidths (ERBs) of auditory filters were not significantly different in young and elderly subjects with normal 2-kHz hearing. Furthermore, filter widths for young subjects with 20- and 40-dB simulated hearing losses overlapped with those obtained from elderly subjects with corresponding degrees of actual hearing loss. These results suggest that the reduced frequency selectivity reported for older listeners can be attributed, primarily, to hearing loss rather than increased age. [Work supported by NIH.]