Manipulating the "straightness" and "curvature" of patterns of interaural cross correlation affects listeners' sensitivity to changes in interaural delay

The purpose of this study was to test the hypothesis that stimuli character ized by "straight" trajectories of their patterns of cross correlation fost er greater sensitivity to changes in interaural temporal disparities (ITDs) than do stimuli characterized by more "curved" trajectories of their patte rns Of cross correlation. To do so, sensitivity to changes in ITD was measu red, as a function of duration, using a set of "reference" stimuli that yie lded differing relative amounts of straightness within their patterns of cr oss correlation while keeping the dominant trajectory at or near midline. T he relative amounts of straightness were manipulated by employing specific combinations of bandwidth, ITD, and interaural phase disparity (IPD) of Gau ssian noises centered at 500 Hz. The results were consistent with expectati ons in that the patterning of the threshold ITDs revealed increasingly poor er sensitivity as greater and greater curvature was imposed on the dominant , "midline," trajectory. The variations in threshold ITD across the stimulu s conditions can be accounted for quite well quantitatively by assuming eit her that the listeners based their judgments on changes in the position of the most central peak of the cross-correlation function or that they based their judgments on changes in the centroid of a second-level cross-correlat ion function. In a second experiment, binaural detection was measured using a subset of the reference stimuli as maskers. As expected, sensitivity was poorest with the maskers characterized by the greatest curvature, which we re also those having the lowest interaural correlation. (C) 2001 Acoustical Society of America. [DOI: 10.1121/1.1327579].