Relating spatial release from masking to lateralization using interaural differences

Abstract

Spatial acoustic cues such as interaural differences in time (ITD) and level (ILD) contribute to the benefit of reduced interference (masking) that occurs when competing sounds (maskers) differ in spatial location from the target talker. This benefit (spatial release from masking or SRM) is well studied but the contributions of ITD and ILD to SRM during speech-on-speech masking remain poorly understood. One hypothesis regarding mixed results in the literature is that SRM primarily reflects differences in overall perceived spatial location rather than independent contributions of ITD and ILD. We evaluated this hypothesis by relating SRM directly to the perceived spatial locations of speech stimuli that were processed in five conditions: ITD only, ILD only, consistent (ITD + ILD), and opposing (ITD – ILD or ILD – ITD). We measured lateralization for speech stimuli in each condition. Lateralization was consistently strongest for consistent ITD + ILD cues, but weaker and more variable across other conditions. Finally, we evaluate a model relating individual differences in SRM to ITD/ILD-based lateralization of target and masker sounds. [Work supported by NIH R01-DC016643]