Lateralization of pulsed sinusoids based on interaural onset, ongoing, and offset temporal differences

When pulsed sinusoids are presented to the ears with an interaural temporal difference but with no rise-decay time or filtering, three values of interaural time are present: onset, ongoing, and offset interaural differences. Lateral discrimination based on interaural temporal differences was studied for such stimuli. The sinusoids were either equal-energy or constant-intensity 65 dB SPL tones. The frequencies of the tones ranged from 150 to 4050 Hz and the durations covered a range of 2 msec-1 sec. The threshold value of interaural time obtained in the lateral discrimination task increased as a function of increasing frequency when intensity was maintained constant. When equal-energy signals were used, the change in lateralization as a function of changes in frequency depended on signal duration. All lateral discrimination thresholds were approximately the same when the onset and offset temporal differences were reduced or eliminated by applying a bandpass filter, high-pass filter, or a rise-decay time, or by presenting the signals with only an ongoing temporal difference. Low-pass filtering the 4050-Hz signals produced lateral discriminations approximately equal to those obtained with no filtering. These results suggest that low-frequency information is the crucial variable for lateralizing sinusoidal stimuli presented with onset, ongoing, and offset interaural temporal differences.