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 threshold for a 1000-Hz pure-tone probe was obtained for six different maskers, which varied in the number of pure-tone components. The masking stimuli consisted of 1, 3, 5, 7, 9, or 11 components, logarithmically spaced in frequency surrounding the signal and presented at a fixed level of 80 dB SPL per component. In most normal-hearing subjects, the threshold for the probe decreased as the number of masking components was increased, demonstrating that stimuli with more components tended to be less effective maskers. Results from hearing-impaired subjects showed no decrease in threshold with increasing number of masking components. Instead, the thresholds increased as more components were added to the first masker. These results appear to be consistent with suppression effects within the multicomponent maskers for the normal subjects and a lack of suppression effects for the hearing-impaired subjects. The results from the normal-hearing subjects are also consistent with "across-channel" cuing.