Consequences of interaural decorrelation of speech temporal fine structure

Abstract

The ability to understand a target speech signal against a background of interfering speech signals is typically improved when the interfering signals are spatially separated (spatial release from masking; SRM). Swaminathan et al. (2016) found a significant reduction in SRM when the temporal fine structure (TFS) across the left and right ears was decorrelated, suggesting that binaural TFS provides important cues that support SRM. One interpretation is that degrading binaural TFS prevents the extraction of reliable interaural time differences (ITDs), which in turn leads to a reduction in SRM. We tested this hypothesis by systematically decorrelating the binaural TFS, and measuring the effects on both ITD discrimination for speech stimuli and SRM in normal hearing listeners. We show that decorrelation leads to a systematic increase in ITD discrimination thresholds, as well as a systematic decrease in SRM. This supports the idea that binaural TFS is needed to access ITD information in speech, which is in turn required for SRM. Additionally, the relationship between these two tasks provides a framework for determining the extent to which reduced SRM in listeners with hearing loss can be attributed to reduced sensitivity to binaural TFS.