Does lateral position explain release from informational masking arising from interaural time and level differences?

Abstract

Spatial release from masking (SRM) is known to arise from the interaural time and level differences (ITDs and ILDs) produced by spatially separated signal and masker sources. In some situations, SRM might be augmented considerably by the differing spatial perceptions created by the signal and masker, which could help alleviate confusions between them. Using headphone presentation, the present study investigated this hypothesized perceptual component of SRM. Maskers were binaural click trains of approximately 2-s overall duration with inter-click intervals (ICIs) varying randomly between 50 and 150 ms. The ITD or ILD of the masker clicks was manipulated across listening blocks. The listeners’ task was to identify the number of signal clicks, identical to the masker clicks except for their ITD/ILD, inserted during masker inter-click intervals. Preliminary testing with a fixed masker ICI demonstrated that the signal clicks were easily audible, strongly suggesting that difficulty during the main identification task was due to confusions from the randomized ICI. The study explored whether performance counting signal clicks in the randomized ICI conditions could be explained by the differences in intracranial spatial perception created by combinations of ITD and ILD cues. [Work supported by NIDCD R01 01625.]