Frequency-Discrimination Performance of Normal-Hearing and Hearing-Impaired Listeners

Abstract

Frequency-discrimination data were obtained for 12 normal-hearing and six hearing-impaired subjects with a 3-interval, 2-cued, yes/no task for a variety of signals. These signals included pure tones, fixed-bandwidth (400 Hz) narrow-band noise and ratio-bandwidth (20%) narrow-band noise. Analyses included response factors in frequency discrimination, comparison of the data from the normal-hearing subjects with published data, relation of the pure-tone and narrow-band noise tasks and performance of the hearing-impaired subjects.

Response factors included criterion as measured by the Beta statistic, sequential effects as described by auto-correlation calculations and learning effects as summarized by the number of practice blocks to stable and asymptotic performance. A wide range of frequency-discrimination results was demonstrated by the normal-hearing subjects and this range appeared to be unrelated to response factor or to threshold as measured by an adaptive 21FC procedure. The results from the hearing-impaired subjects overlapped those of the normal-hearing subjects in a number of cases and the response factors (learning, sequential effects and response criterion) were found to be very similar for both subject groups. With the hearing-impaired subjects, the relation between magnitude of hearing loss and difference limen was strongest for the 5000-Hz signals and weakest for the 500-Hz signals.

A prediction equation was derived from multiple-regression analysis which accounted for approximately 91% of the variance in frequency-discrimination performance across the 18 subjects with three factors (frequency, sensation level, and signal bandwidth) and a constant. Hearing loss affected the comparisons between pure-tone and narrow-band noise difference limina by making the differences between these smaller than would be expected from the data of the normal-hearing subjects.