Perception of Steady and Intermittent Sounds with Alternating Noise-Burst Stimuli

Abstract

Bursts of high-pass filtered thermal noise coming from two different sources in space were alternated in time (with no time gap between bursts). Separation angles between sources from 5 to 50 deg were used, and alternation rates from 2 to 14 per sec. Duration of bursts was also varied. Subjects indicated for each sound perceived whether it was steady or intermittent, and where it was located. When the angle between sources is small, some subjects may hear only one continuous sound, provided that the repetition rate is relatively high. More commonly, however, our subjects tend to hear one steady sound and one intermittent sound when the separation angle between sources is small; they tend to hear this pattern at wider separation angles when the duration of one of the stimuli is short. When one of the bursts has short duration, and sources are separated by 30 to 50 deg, it appears to many subjects that the short burst is markedly displaced in location. For wider angles of separation between sources, and various conditions of duration, many subjects can also hear a third steady sound between the other two. Occurrence of this latter sound has especially interesting implications for a theory of sound-localization mechanisms.