Just discriminable change of velocity of a simulated moving sound source

Abstract

The Doppler effect refers to the frequency change observed for a moving sound source. The listener will observe a higher than emitted frequency in front of the moving source and a lower frequency behind it. Although the existence of the Doppler effect has been long documented, relatively little experimental work has investigated the human perceptual response to frequency and intensity changes due to moving sound sources. This experiment determined the just discrminable change of velocity of a computer simulated moving sound source. Subjects were tested at 500, 1000, and 4000 Hz for reference velocities of 1, 2, 4, and 8 m/s. Signal duration was 500 ms. A 2-Q,2-AFC adaptive procedure determined the listener’s velocity difference limen (DL). At 500 Hz, the smallest DL was 10.46 m/s at reference velocity 8 m/s. The DL increases as the reference velocity decreases. This pattern is evident at all tested source frequencies. Weber fractions were calculated for both velocity DLs and frequency deviation. The results indicate that both velocity DL and frequency deviation increase as reference decreases, signifying that Weber’s law does not hold for source velocity and frequency. [Work supported by a College of Arts and Sciences Honors Scholarship and a grant from the College of Social and Behavioral Sciences.]