Upper Limits of Auditory Motion Perception: the Case of Rotating Sounds

We report two experiments investigating rotating sounds presented on a circular array of 12 speakers. Velocity thresholds were measured for three different types of stimuli (broadband noises, white noise, harmonic sounds). In the first experiment, we gradually increased or decreased the velocity and asked participants to indicate the point at which they stopped or started (respectively) perceiving a rotating sound. The thresholds ranged between 1.95-2.80 rot/s for noises and 1.65-2.75 rot/s for harmonic sounds. We observed significant effects of the direction of velocity change (acceleration or deceleration), stimulus type and fundamental frequencies for harmonic sounds, but no effect of centre frequency was observed for broadband noises. In the second experiment, stimuli were presented at constant velocities in a single-interval forcedchoice paradigm: listeners were asked to indicate if the sound was rotating or not. The thresholds obtained were within the range of those of the first experiment. The effect of frequency for harmonic sounds was confirmed.