Lateral position and across-frequency envelope coherence

Abstract

The relationship between across-frequency and across-ear (binaural) information was varied in an effort to determine the relative locus of the two processes. Interference effects might be expected if the output from one system influences the input to the other. In the first experiment, observers indicated whether the envelopes of 200-ms, 100-Hz-wide bands of noise, centered at 2000 and 5000 Hz, were identical or statistically independent. The lateral positions of the two bands of noise were either the same or varied independently via interaural intensity differences (IID). No difference was observed. The second experiment measured threshold IID values for a 100-Hz-wide band of noise centered at 2000 Hz that was presented either with or without a 100-Hz-wide distractor band centered at 5000 Hz. The distractor band had an envelope that was either identical to or independent of the envelope of the target band. Although adding a distractor band produced some increase in threshold, the threshold did not depend on envelope similarity. The lack of interference suggests that these two processes proceed independently. [Work supported by the National Institutes of Health.]