The combination of interaural information across frequencies: the effects of number and spacing of components, onset asynchrony, and harmonicity.

Threshold interaural delays were measured for a single interaurally delayed low-frequency target component presented against a background of two, four, six, or eight diotic "distractor" components. In the first experiment, a 753-Hz target and the flanking distractor components were gated on and off simultaneously. In subsequent experiments, the distractors were gated on 25-200 ms prior to the target. In addition, the target and distractor components were given various harmonic configurations. In general, threshold interaural delays were higher in all conditions in which distractors were present relative to thresholds obtained for the target component in isolation. Subjects reported that the pitch of the target component was more salient when an onset asynchrony between the target and distractors was present, but the components were perceived as occupying a single intracranial position in spite of the various interaural delays across the frequency domain. These results suggest that binaural processing of stimuli consisting of a small number of low-frequency temporally overlapping components occurs in a spectrally synthetic manner in which interaural information is combined across the spectrum, even in situations in which the segregation of pitch information occurs.