Lateralization of bands of noise: effects of bandwidth and differences of interaural time and phase.

Abstract

The effects of stimulus bandwidth on lateralization of narrow bands of noise were investigated with an acoustic pointing task. Stimuli were narrow bands of noise (centered on 500 Hz with bandwidths ranging from 50-400 Hz) that contained interaural time delays and/or interaural phase shifts. The overall extent of lateralization and sidedness was found to vary greatly as a function of stimulus bandwidth, as insightfully discussed earlier by Jeffress [L. A. Jeffress, Foundations of Modern Auditory Theory, edited by J. V. Tobias (Academic, New York, 1972)]. The data are qualitatively consistent with a weighted-image model [Stern et al., J. Acoust. Soc. Am. 84, 156-165 (1988)] that specifies and utilizes the shapes and locations of patterns of hypothesized neural activity. These patterns are topographically organized along a two-dimensional surface, and they describe the cross-correlation function of the stimuli as a joint function of frequency and the delay parameter of the cross-correlation operation. In this fashion, lateralization depends upon individual modes of such patterns that are weighed with respect to their straightness (consistency of interaural delay over frequency) and centrality (the extent to which interaural delays are small in magnitude).