Thomas Z. Strybel
Dept. of Psychol., California State Univ., Long Beach, CA 90840
The range of stimulus durations and interstimulus onset intervals (ISOIs) that produced the illusion of auditory apparent motion (AAM) were measured when two sound sources were separated in either the horizontal or median planes. Three speaker arrangements were tested, 350(degrees) and 10(degrees) azimuth at 0(degrees) elevation, 0(degrees) and 180(degrees) azimuth at 0(degrees) elevation, and 0(degrees) and 20(degrees) elevation at 0(degrees) azimuth. Subjects were instructed to categorize their perception of the stimulus sequence into one of five categories that were based on the number of sources heard and whether or not motion was perceived. Subjects also indicated the relative location of the leading stimulus. For each speaker arrangement, stimulus durations of 10, 25, and 50 ms and ISOIs between 2 and 70 ms were tested. The plane in which the sources were located did not affect the timing conditions that produced the illusion of motion. AAM was heard for stimulus durations of 25 and 50 ms at ISOI values that were roughly equal to stimulus duration for all of the speaker arrangements tested. However, judgments of the location of the leading source were affected by the arrangement of the speakers. Performance on this task was best when the sources were separated in the horizontal plane.