Minimum auditory movement angle: binaural localization of moving sound sources.

In the first experiment, subjects were asked to discriminate whether a sound was emanating from a moving or stationary source. The minimum audible movement angle (MAMA) thus defined was observed to increase as the source velocity increased. MAMA ranged from a low of 8.3 degrees with the slowest velocity employed (90 degrees/s) to a high of 21.2 degrees with the fastest velocity (360 degrees/s). In the second experiment, subjects were asked to localize where the moving source was, at signal on and offset. The results indicate that the apparent onset is displaced in the direction of motion and the amount of this displacement is directly related to source velocity. Less consistent results were observed with signal offset. The present results suggest that the binaural system is relatively insensitive to motion.