Interactions between hearing loss and the spectral overlap of competing sounds in masked speech intelligibility.

Abstract

This experiment explored the ideas that energetic masking (EM) limits the benefit achievable from spatial separation in a competing speech task and that differences in EM between normal-hearing (NH) and hearing-impaired (HI) listeners can explain differences in spatial release from masking (SRM). Target sentences and similar masker sentences (or in another condition, masker noises) were filtered into four narrow spectral bands and presented simultaneously. The spectral overlap of the target and masker bands was varied from minimal (interleaved bands) to maximal (identical bands). Both NH and HI listeners showed spectral tuning, such that masking by noise or speech was reduced as spectral overlap was reduced. In fact, this signal processing often improved intelligibility relative to that seen with unfiltered speech. Moreover, thresholds in the noise and speech maskers were closely related, suggesting that EM was the main factor limiting performance across tasks. More masking was found in HI as compared to NH listeners for all spectral overlaps and both maskers, and the HI group generally had less SRM. However, variations in spectral overlap did not lead to dramatic changes in SRM or in the difference in SRM observed between groups.