Cue-reversal points and interaural time JND's at various frequencies

Abstract

Previous research on the lateralization of a 500-Hz tone as a function of interaural delay T has suggested that there exists a delay T0 (usually in the vicinity of 700 μs) that divides the interval 0 ⩽ T ⩽ 1 ms into two regions: the region 0 ⩽ T ⩽ T0, where an incremental increase in T causes the binaural image to move farther to the side, and the region T0 ⩽ T ⩽ 1 msec where an incremental increase in T causes the image to move back towards the center [Hershkowitz and Durlach, J. Acoust. Soc. Am. 46, 1464–1467 ( 1969)]. This critical delay To is referred to as the “cue-reversal” point. We are conducting experiments employing 21, 2AFC procedures and acoustic monitoring to explore the dependence of cue-reversal points on frequency f. In these experiments, no feedback is given and the subjects are required to judge whether the addition of an increment ΔT to T causes the image to move toward or away from center. Preliminary results indicate that (1) the values of T0 on the right and left are often unequal and (2) the cue-reversal phenomenon is incomplete in the sense that lateralization performance in the region T0⩽T⩽12f is less consistent than performance in the region 0 ⩽ T ⩽ T0. We also plan to investigate, using a similar paradigm with feedback, interaural time jnd's in the vicinity of the cue-reversal point. [Work supported by NIH.]