Perceptual simultaneity range as a function of frequency separation for two pure tones

Abstract

This paper provides a phenomenological quantitative function of the perceptual simultaneity range (PSR) in terms of the frequency separation and a possible explanation. The PSR for two pure tones was measured with the frequency separation between the tones from 0.07 to 4.09 octaves with the lower frequency fixed at 200 Hz. In this study, listeners judged the simultaneity of the tones using the perceptual synchrony–asynchrony cue while the possible use of the perceptual fusion–separation cue (``oneness'' or ``twoness'') was eliminated. Results show that the PSR plotted against the frequency separation can be fitted to two segmented linear regression lines, one decreasing for small frequency separation and the other increasing for large frequency separation. These regression lines intersect around the critical bandwidth. Results also show no effects of the frequency separation on the singular interval or points, such as tonal consonance, musical consonance, and harmonic relations. These results suggest that the perception of simultaneity is mainly determined by the peripheral representation of the tone distance. We propose a possible explanation for the behavior of the PSR for small frequency separation by considering the mechanics of basilar membrane motion. However, the explanation for the behavior for large frequency separation is still unclear.