On the influence of interaural differences on temporal perception of masked noise bursts

In this research, the influence of interaural differences on temporal positioning of the perceived onset of a dichotic broadband noise target in a diotic broadband noise masker was explored. Interaural time or level differences, a combination of these differences, and filtering with head-related transfer functions were applied to broadband noise bursts, to establish lateralization in quiet at center and right positions in the lateral plane. While applying these interaural differences, the subjects' ability to accurately align the noise's onset to the meter of a regular series of diotic reference onsets was investigated for various signal-to-noise ratios. At high target sensation levels, mean onset positions were close to physical isochrony and no systematic differences in temporal positioning due to different interaural cues were observed. At low target sensation levels, positioning accuracy decreased with a decreasing signal-to-noise ratio, and dichotic targets were positioned less accurately than diotic targets. This reduced temporal positioning accuracy could not be attributed to differences in detectability of the targets just above the threshold, nor to a reduction of effective target bandwidth of dichotic broadband targets. From these results, the reduced accuracy of temporal perception in binaural unmasking conditions may be seen as a consequence of temporal integration in binaural processing.