Existence region of dichotic noise pitch

Abstract

In several forced-choice experiments, listeners were required to discriminate a 400-msec burst of diotic noise from a 400-msec burst of dichotic noise. Both noises were computer synthesized, and were produced by adding (digitally) equal-amplitude, random-phase sinusoids, spaced 10 Hz apart from 100 to 3000 Hz. The dichotic noise was identical to the diotic noise except that one component (the “signal”) was interaurally phase reversed. In some conditions several, harmonically related, components were phase reversed. As is well known, such dichotic noise stimuli produce a pitch that corresponds to the frequency which is phase reversed, and this pitch was presumably the basis of discrimination in our experiments. The aim of the experiments was to determine the frequency limits (existence region) for the dichotic noise pitch. For “signals” between about 200 and 100 Hz, discrimination performance was near perfect, and beyond these limits dropped abruptly to chance. Moreover, it appeared that adding harmonics to the “signal” affected perception of the fundamental pitch only to the extent that the harmonics themselves were within the critical frequency region. These results suggest that the dichotic noise pitch is mediated by the same sort of process that underlies the masking-level-difference (MLD) phenomenon.