Rapid binaural processing for source segregation and lateralization

Abstract

For realistic listening conditions, interaural cues will fluctuate due to the presence of multiple active sources. If it is assumed that the binaural system is sluggish, then the perceived location of the sound input would be an average of the varying interaural cues. If, however, the binaural system is fast enough to assess the rapidly changing interaural differences, then it could be possible for the binaural system to properly identify the spatial position of a target source. Using a continuous, broadband noise stimulus that contained periodically alternating interaural time differences (ITD) and, notably, no monaural cues, we investigated the binaural system's ability to lateralize brief durations of the target ITD. Results show that listeners can lateralize targets for durations of 3–6 ms indicating that the binaural system allows for a segregation and lateralization of the target and interfering noise streams. Furthermore, results indicate that the binaural system mediates the buildup of a modulated stream. A second experiment investigating whether the salience of the target ITD in the aforementioned stimulus depends on the temporal position of the target within the phase of an amplitude modulated envelope revealed that this was not the case.