Wen Wang
Dept. of Psychol., Univ. of Wisconsin, Madison, WI 53706
Robert A. Lutfi
Univ. of Wisconsin, Madison, WI 53705
An experiment was conducted to determine if listeners, when judging the velocity and acceleration of a sound-emitting source, merely infer these quantities from overall source displacement. The acoustic waveform of a high-velocity source was reconstructed over headphones using principles of sound radiation and propagation from the moving source, an interaural time difference method, and a diffraction model of a spherical head. An adaptive 2IFC procedure was used to measure thresholds for detection of a change in the displacement, velocity, and acceleration of the source passing directly in front of the listener in a linear trajectory from left to right. The source traveled at 50 m/s for 4 s, at a distance of 5 m from the center of the head, point of closest approach. Thresholds for a rightward displacement showed little variability across listeners, averaging about 7 m. Velocity and acceleration thresholds varied from one listener to the next, but were in some cases less than the minimum value that could be inferred given the 7-m threshold for displacement. The results are discussed in terms of cues for discrimination related to changes in intensity, interaural delay, and Doppler effect. [Research supported by NIDCD.]