The relative salience of auditory motion cues

The relative salience of auditory motion cues was measured in a series of four experiments. In the first three experiments, all combinations of three different auditory motion cues (intensity changes, Doppler frequency shifts and interaural time delays) were presented at various source trajectories, parallel to the listener's frontal plane. In the first experiment, the velocity of the source was varied from 7.5 to 100 miles per hour and the point of closest passing was varied from 1 to 100 meters. In the second experiment, the angular position of the source always moved from minus 30 degrees to plus 30 degrees and the minimal distance of the path was varied. In the third experiment, the simulated velocity was fixed at 33 miles per hour for all stimuli. The results of these experiments show that monaural acoustic cues of intensity and Doppler frequency changes had the greatest effect on the listeners' judgments of perceived velocity. The binaural cue of interaural time delays had little effect on the velocity judgments. The results also show that the distance traveled by the source was found to be a more salient velocity cue than actual sound source velocity. A fourth experiment was conducted to measure speed estimates of actual moving automotive sounds via dummy-head recordings. Actual sounds were estimated to travel at greater velocities than were simulated sounds, especially when the sounds were far away from the listener.