Auditory apparent motion between sine waves differing in frequency.

The effects of frequency differences between the lead and lag stimuli on auditory apparent motion (AAM--the perception of continuous changes in the location of a sound image over time) were examined in two experiments. In experiment 1, three standard frequencies (500, 1000, and 5000 Hz) and three SOAs (40, 60, and 100 ms) were tested. Both standard frequency and stimulus onset asynchrony (SOA) were constant throughout a session. Eleven comparison frequencies were tested within each session, with the range dependent on the standard frequency. At standard frequencies of 500 and 1000 Hz, AAM was heard when the frequencies of the lead and lag stimuli were within 100 Hz of each other. At 5000 Hz, the range of frequencies producing AAM increased with SOA. In experiment 2, two standards (500 and 5000 Hz) were tested with a wider range of SOAs (10-210 ms) varied within a session, and a narrower range of comparison frequencies. Here, comparison frequency was constant throughout a session. At 500 Hz, the SOAs producing AAM did not depend on comparison frequency. At 5000 Hz, the SOAs producing AAM increased with comparison frequency, consistent with Korte's third law of visual apparent motion.