Effects of phase changes in low‐numbered harmonics on formant frequency matches

Abstract

Phase changes to single harmonics (of a 125‐Hz fundamental) in the first formant (F1) region can change the phoneme boundary between /I/ and /e/ along an F1 continuum in an identification task [C. J. Darwin and R. B. Gardner, J. Acoust. Soc. Am. 79, 838–845 (1986)]. Physiological correlates of this effect have been noted in the ALSR response of guinea‐pig auditory nerve fibers [A. R. Palmer et al., in The Psychophysics of Speech Perception, edited by M. E. H. Schouten (Nijhoff, Dordrecht, 1987)] and in an auditory model with synchrony suppression. The present work demonstrates similar phase effects using a matching paradigm. Subjects matched sounds along a continuum that differed in F1 frequency and could have additional formants. The target sounds (fundamental = 125 Hz; F1 = 440 Hz) were taken from the matching continuum but had the phase of a single harmonic changed. Systematic and consistent differences in the matched F1 value were found as a function of phase. Although the starting phase of the components influenced the size of the matched difference in F1, the difference was still present for randomized starting phases. The effect required at least three frequency components and varied with fundamental frequency.