Accruing binaural cues across frequency

Abstract

Localizing a complex sound requires in part an analysis of the interaural difference of time (IDT) of the component frequencies. Above about 500 Hz, the IDT is constant across the frequency spectrum. This commonality may be used to group components that arise from a single source as well as segregating such components from those which arise from competing sources. Interactions across components can be shown by measuring changes in IDT thresholds when a target is lateralized in the presence of other simultaneous sounds. When the nontarget sound has a dissimilar IDT, thresholds may actually increase. This effect has been aptly termed “interference” [D. McFadden and E.G. Pasanen, J. Acoust. Soc. Am. 59, 634–639 (1976)]. In the present experiment, listeners detected an IDT in a 600-Hz target tone both with and without the presence of a nontarget tone. Of special interest was the harmonic relation between target and nontarget. Among other factors, the results show that a simple relation such as 400 Hz can produce more interference than one that is nonharmonic, even when the interfering tone is closer to the target, e.g., 531 Hz. [Research supported by NIH.]