Temporal resolution of frequency-modulated signals by hearing-impaired listeners

Abstract

Hearing-impaired and normally hearing subjects were asked to discriminate between two sinusoidal signals. One signal, the glide, moved from its initial frequency over a linear path to its final frequency. The other, the step signal, was the same except that its trajectory followed a series of discrete steps in frequency. As the number of steps increased, the duration of the individual steps decreased, and the signal more closely resembled the glide. The center frequencies of the signals were 0.5, 1.0, 2.0, and 4.0 kHz. The signals were presented to the two groups at equal SLs and at equal SPLs. The impaired subjects exhibited significantly poorer discrimination than the normally hearing subjects, indicating a reduced ability to temporally resolve the step modulation. A frequency effect was evident in both groups, with much poorer resolution at 4.0 kHz. A level effect was noted in the normal subjects, who exhibited poorer resolution at higher SPLs. The results from the normally hearing subjects were very similar to temporal resolution values obtained in previous studies using amplitude-modulated (gapped) sinusoids. [Work supported by a grant from AFOSR.]