Lateralization of complex waveforms: Effects of fine structure, amplitude, and duration

Abstract

In recent years there has been an increased interest in the use of interaural time as a cue for lateralization at high frequencies. Our study examines this question using AM complexes with carriers of 1800, 2400, 3000, 3600, 3900, 4200, and 4500 Hz, modulated at 300 Hz and interaurally delayed. The findings indicate that (a) the ability to lateralize these stimuli does not depend on low-frequency distortion, since this ability remains despite the presence of intense low-frequency masking; (b) the task is easier when the entire waveform, rather than just the modulation envelope, is delayed, though this difference seems to decline with practice; (c) the effects of stimulus amplitudé and duration on the detection of interaural time differences are reminiscent of those observed with pure tones, although ongoing time differences may be more fully utilized with AM signals; and (d) lateralization declines with interaural carrier frequency discrepancy. We were unable to obtain lateralization of AM complexes at one ear against pure tones (at the modulation frequency) at the other. This strengthens the argument that all stimulus information used is carried in high-frequency channels. © 1976, Acoustical Society of America. All rights reserved.