The auditory motion aftereffect: its tuning and specificity in the spatial and frequency domains

In this paper, the auditory motion aftereffect (aMAE) was studied, using real moving sound as both the adapting and the test stimulus. The sound was generated by a loudspeaker mounted on a robot arm that was able to move quietly in three-dimensional space. A total of 7 subjects with normal hearing were tested in three experiments. The results from Experiment 1 showed a robust and reliable negative aMAE in all the subjects. After listening to a sound source moving repeatedly to the right, a stationary sound source was perceived to move to the left. The magnitude of the aMAE tended to increase with adapting velocity up to the highest velocity tested (20 degrees/sec). The aftereffect was largest when the adapting and the test stimuli had similar spatial location and frequency content. Offsetting the locations of the adapting and the test stimuli by 20 degrees reduced the size of the effect by about 50%. A similar decline occurred when the frequency of the adapting and the test stimuli differed by one octave. Our results suggest that the human auditory system possesses specialized mechanisms for detecting auditory motion in the spatial domain.