The auditory aftereffects of radial sound source motion with different velocities

Auditory aftereffects were evaluated after short adaptation to radial sound source motion with different velocities. Approach and withdrawal of the sound source were imitated by means of rhythmical noise (20 Hz-20 kHz) impulse sequences with arising or diminishing amplitude. They were presented in an anechoic chamber through two loudspeakers placed at 1.1 and 4.5 m from the listener. The adapting stimulus velocities were 0.68, 3.43, 6.92 and 9.97 m/s at adaptation duration of 5 s. By every adaptor speed an aftereffect revealed as distinguishing of psychometric function at approaching and withdrawing adaptors. The direction of function displacements was opposite to one of adaptor motion. Three parameters reflecting alteration of perception after motion adaptation were determined and were compared with control data: an evaluation of stationary test stimuli; a velocity of moving test signal at the point of subjective equality (perceptually unmoving point); a percentage of responses after averaging across all test signals. These parameters of auditory radial motion aftereffect have similar tendencies to change with adaptor velocity. They have demonstrated significant effect at slow motion (0.68 and 3.43 m/s) and small effect at quick motion (6.92 and 9.97 m/s).