ONSET DOMINANCE IN LATERALIZATION

Saberi and Perrott [Acustica 81, 272-275 (1995)] found that the in-hea d lateralization of a relatively long-duration pulse train could be co ntrolled by the interaural delay of the single pulse pair that occurs at onset. The present study examined this further, using an acoustic p ointer measure of lateralization, with stimulus manipulations designed to determine conditions under which lateralization was consistent wit h the interaural onset delay. The present stimuli were wideband pulse trains, noise-burst trains, and inharmonic complexes, 250 ms in durati on, chosen for the ease with which interaural delays and correlations of select temporal segments of the stimulus could be manipulated. The stimulus factors studied were the periodicity of the ongoing part of t he signal as well as the multiplicity and ambiguity of interaural dela ys. The results, in general, showed that the interaural onset delay co ntrolled lateralization when the steady state binaural cues were relat ively weak, either because the spectral components were only sparsely distributed across frequency or because the interaural time delays wer e ambiguous. Onset dominance can be disrupted by sudden stimulus chang es within the train, and several examples of such changes are describe d. Individual subjects showed strong left-right asymmetries in onset e ffectiveness. The results have implications for understanding how onse t and ongoing interaural delay cues contribute to the location estimat es formed by the binaural auditory system. (C) 1997 Acoustical Society of America.