Auditory temporal acuity in hearing-impaired listeners for frequency-modulated signals

Abstract

Recent studies of auditory temporal acuity in the hearing impaired have tended to focus on the resolution of amplitude modulation. This study compares the temporal resolution of normal and hearing-impaired subjects in an experimental paradigm using frequency-modulated stimuli. Three hearing-impaired and three normally hearing subjects had to distinguish two sinusoidal signals. The first, the glide signal, moved from its initial frequency over a linear path to its final frequency. The second, the step signal, was the same except that its trajectory followed a series of discrete steps in frequency. As the number of steps in the step signal increased, the duration of the individual steps decreased, and the signal more closely approximated the glide. The center frequencies of the signals were 500, 1000, and 4000 Hz. The subjects were asked to identify the interval containing the step signal in a 2-Q, 2AFC task. When the signals were presented at equal sensation levels, the impaired subjects exhibited significantly poorer discrimination than the normally hearing subjects, indicating a reduced ability to resolve the step modulation. Implications for formant processing by the hearing impaired will be discussed. [Work supported by a grant from AFOSR.]