Effects of differences in fundamental frequency on cross-formant grouping in speech perception.

Abstract

In isolated syllables cross-formant perceptual grouping can be promoted by a common fundamental frequency (F0), but this effect is relatively weak [Darwin, Q., J. Exp. Psychol. 33A, 185–207 (1981)]. Few studies have explored the role of F0 in cross-formant grouping using sentences. Three-formant (F1+F2+F3) analog of almost continuously voiced natural utterances were synthesized using a monotonous glottal source (F0=150 Hz). Perceptual organization was probed by presenting stimuli dichotically (F1+F2C+F3; F2), where F2C is a competitor for F2 that listeners must resist to optimize recognition. Competitors were created using time-reversed amplitude and frequency contours of F2, and F0 was manipulated (ΔF0 = ±8, ±2, or 0 semitones relative to the other formants). Adding F2C reduced intelligibility for most utterances, and this reduction was greatest overall when ΔF0=0. However, as for isolated syllables, the effect of ΔF0 was quite small. Competitor efficacy was also somewhat dependent on absolute F0. Manipulation of relative F2C level indicated that competitor efficacy was not due primarily to energetic masking. The modest effect of ΔF0, both for sentences and isolated syllables, suggests that cross-formant grouping depends more on other factors, for example common patterns of modulation. [Supported by EPSRC]