The effects of differences in burst duration and rise/decay time on auditory apparent motion in the free field

This study examined the effects of differences in burst duration and rise/decay time between the lead and lag stimuli on auditory apparent motion (AAM: the illusion of motion produced by the proper timing between two stimuli). Three standard burst durations (25, 100, and 400 ms) with 0-ms rise/decay times were each employed with three stimulus onset asynchronies (SOAs) that produce continuous motion for lead and lag stimuli of equal durations. During a trial block, five variable burst durations (25, 50, 100, 200, and 400 ms) and two rise/decay proportions (.00 and .15) were tested. On half the trials the standard burst was presented first. The signals were high-pass noise, and they were presented from two loudspeakers at ±20° azimuth. AAM was heard most often when the duration of the lead and lag stimuli were equivalent. The SOAs that produced AAM depended on the duration of the lead source only. No significant effects of rise/decay proportion were observed.