Detection of interaural decorrelation in multitone complexes

The present study examined the ability of listeners to detect interaural decorrelation of multicomponent complexes. Just-noticeable correlation differences for a reference correlation of + 1.00 were measured as a function of the number of components in the complex (3,5,9) and bandwidth of the complex (20, 40, 80 Hz). All components were equally spaced and centered at 753 Hz. A 2IFC procedure was used, in which the first interval consisted of a complex with an interaural correlation of + 1.00 (i.e., a diotic complex), and the second interval contained either a diotic complex or an interaurally decorrelated complex. The complexes were decorrelated by generating interaural phase differences (IPDs) in the individual components. The lowest frequency component had an IPD of 0, while the remaining components had equal magnitude IPDs that were of opposite sign for adjacent components. Thus, for each n-component complex, n − 1 components carried an IPD in the decorrelated intervals. The starting phases of the components were randomized between intervals. All of the observed threshold interaural correlations were greater than 0.99 in all conditions. Thresholds were lowest for the 80-Hz bandwidth conditions for three, five, and nine components. At each bandwidth, thresholds increased with increasing numbers of components. [Work supported by NIH.]