Effects of phase changes in low-numbered harmonics on the internal representation of complex sounds

A series of experiments investigated the effect of phase changes in lownumbered single harmonics in target sounds that were either synthesized steady-state vowels or periodic signals having only a single formant. A matching procedure was used in which subjects selected a sound along a continuum differing in first formant frequency in order to get the best match with the target sound; perceptual effects of the phase manipulations in the target were detected as a change in the matched first formant frequency. Stimuli had to contain at least three harmonics to produce the effect, but it did not require a particular starting phase of the components. A suppression phenomenon is discussed, in which phase changes alter the phase-locking characteristics of auditory fibres tuned to low-numbered harmonics.