Detection of tones in modulated noise: Effects of masker level and masker depth.

Abstract

It is possible to estimate temporal resolution at discrete spectral locations by subtracting the masked threshold produced by a modulated masker from that produced by an unmodulated masker (the difference is referred to as the modulated-unmodulated difference, or MUD). This paradigm may be especially useful for measuring temporal resolution in subjects with hearing loss, provided that the MUD is independent of level. The purpose of the present study was to examine the MUD as a function of masker level at several signal frequencies. In the first experiment, the sinusoidally amplitude-modulated masker had a depth (m) of 1.0. The MUD increased by as much as 15 dB as the spectrum level of the masker increased from 0 to 40 dB SPL. In the second experiment, the modulated masker had a depth of 0.75 or 1.0. When the masker depth was 1.0, the MUD increased with increasing masker level, as in experiment one. When it was 0.75, however, the MUD — though reduced — was essentially independent of masker level. These results suggest that a masker depth of 0.75 may be used to compare temporal resolution between normal-hearing and hearing-impaired subjects without being complicated by effects of masker level. [Work supported by NIDCD.]