Effects of rise/decay time on the lateralization of interaurally delayed 1-kHz tones

Experiments in lateralization were performed to evaluate the relative contribution of onset and phase cues in binaural hearing. A 1-kHz signal was presented with interaural stimulus delays ranging from 0 to 1000 microseconds, corresponding to phase shifts of 0 degree to 360 degrees. For a given value of delay, the leading signal was presented randomly to the right or left ear over a block of 100 trials, and the laterality of the resultant image was judged. The percentage of correct judgments was plotted as a function of delay with rise/decay time as a parameter. Values of rise/decay time ranged from 0 to 500 ms. The results indicated that rise/decay times of at least 200 ms are necessary to avoid contributions from the onset cue to the formation of lateralization judgments. For rise/decay times shorter than 200 ms, a conflict occurs between phase and onset cues in the region of phase shifts from 180 degrees to 360 degrees. At the limit with very short rise/decay times, the onset cue completely overrides the phase cue.