Pitch discrimination for multiple simultaneous complexes: Effects of harmonic resolvability

Abstract

In natural listening contexts, especially in music, it is common to hear three or more simultaneous pitches, each defined by a harmonic complex tone. In order to extract the pitches of these tones using the rate-place code, peripherally resolved components are required, but the peripheral resolvability of a complex tone is reduced when multiple pitches are presented. In this experiment, we investigated the effect of resolvability on pitch discrimination in the context of multiple pitches. Listeners were asked to discriminate the direction of a 0.5-semitone pitch change at the end of a four-tone sequence, where the last tone in the sequence was embedded in a mixture of two other simultaneous tones. Tones were either pure tones, or complex tones filtered into one of two bandpass regions, in order to manipulate the extent to which harmonics were resolved both before and after mixing. Discrimination performance was significantly above chance, even in the high-frequency region where the combination of harmonic components should have been unresolved after mixing, suggesting that resolved harmonics may not be necessary to extract the pitch from multiple complex tones. Predictions from spectral and temporal models of pitch were compared with the results. [Work supported by NIH grant R01DC005216.]