Perception of the [m]-[n] distinction in VC syllables

This study complements earlier experiments on the perception of the [m]-[n] distinction in CV syllables [B. H. Repp, J. Acoust. Soc. Am. 79, 1987-1999 (1986); B. H. Repp, J. Acoust. Soc. Am. 82, 1525-1538 (1987)]. Six talkers produced VC syllables consisting of [m] or [n] preceded by [i, a, u]. In listening experiments, these syllables were truncated from the beginning and/or from the end, or waveform portions surrounding the point of closure were replaced with noise, so as to map out the distribution of the place of articulation information for consonant perception. These manipulations revealed that the vocalic formant transitions alone conveyed about as much place of articulation information as did the nasal murmur alone, and both signal portions were about as informative in VC as in CV syllables. Nevertheless, full VC syllables were less accurately identified than full CV syllables, especially in female speech. The reason for this was hypothesized to be the relative absence of a salient spectral change between the vowel and the murmur in VC syllables. This hypothesis was supported by the relative ineffectiveness of two additional manipulations meant to disrupt the perception of relational spectral information (channel separation or temporal separation of vowel and murmur) and by subjects' poor identification scores for brief excerpts including the point of maximal spectral change. While, in CV syllables, the abrupt spectral change from the murmur to the vowel provides important additional place of articulation information, for VC syllables it seems as if the format transitions in the vowel and the murmur spectrum functioned as independent cues.