Lateralization Predictions for High-Frequency Binaural Stimuli

Revised Abstract The position-variable model [R.] is extended to describe the subjective lateral position of amplitude-modulated tones and bandpass noise, as well as other complex stimuli that are presented within spectral regions at which the binaural system appears to be unable to make use of cycle-by-cycle interaural temporal differences. Predictions of the model are based on the centroid of the crosscorrelation of the hypothetical auditory-nerve response to the stimuli, which is either calculated using analytical techniques or simulated numerically. The model of auditory-nerve activity, which is typically used to describe the response to stimuli at lower frequencies, also extracts envelopes of higher-frequency stimuli, as discussed previously by Colburn and Esquissaud. This information appears to be useful in predicting the lateral position of such high-frequency stimuli. Preliminary results indicate that the model is able to describe most of the ways in which the laterality of high-frequency AM tones and bandpass noise with low-frequency envelopes depends on modulation frequency, carrier frequency, and other stimulus parameters. The model also predicts the "dominant region" effect (describing the relative salience of interaural temporal cues at different frequencies), as well as counterintuitive reversals in lateralization of rectangularly-modulated bandpass noise stimuli. Important results not yet described by the model include the specific carrier frequency at which AM tones exhibit the greatest laterality with a fixed waveform delay, and the relative laterality of high-frequency AM tones and bandpass noise with narrow bandwidth.