Forward-masking properties of multicomponent signals in normal and hearing-impaired subjects

The forward-masking properties of inharmonic complex stimuli were measured both for normal and hearing-impaired subjects. The signal was a single sinusoid of 1000 Hz. Signal threshold was obtained for six different maskers that varied in the number of components. Masking stimuli consisted of 1, 3, 5, 7, 9, or 11 components, logarithmically spaced in frequency surrounding the signal, and were presented at a fixed level of 80 dB SPL per component. An adaptive two-alternative forced choice method was used to determine thresholds. In normal-hearing subjects, the threshold for the signal decreased as the number of components was increased, demonstrating that signals with more components are less effective maskers. Results from hearing-impaired subjects indicated no decrease in threshold with increasing masking components, instead, the thresholds increased as more components were added to the first masker. [Work supported by the Deafness Research Foundation and the Whitaker Foundation.]