Evidence against acoustic invariance in initial voiced stop consonants

Abstract

A perceptual experiment was conducted with naturally spoken intitial stop consonants in order to test recent claims for acoustic invariance in the initial portions of stop consonants [for example, S. E. Blumstein and K. N. Stevens, J. Acoust. Soc. Am. 67, 648–662 (1980)]. The original stimuli consisted of tokens of the stops /b,d,g/ with the vowels /i,a,u/ as spoken by two male and two female speakers. A computer graphics waveform editor was used to locate the initial portions of the waveform up to the first, second, fourth, and sixth voicing pulses. Three experimental conditions were evaluated: (a) the initial segment only; (b) the initial segment plus the original steady-state vowel; and (c) the intitial segment plus an alternate steady-state vowel. Ten listeners participated in a forced-choice recognition experiment to determine the conditions for which perceptual cues to consonant identity are retained. Recognition accuracy was consistently highest for condition (b), lower for condition (a), and lowest for condition (c). These results, therefore, argue against vowel-independent cues to stop consonant recognition and are more consistent with studies which conclude that the perception of stop consonants is strongly influenced by the following vowel [for example, M. F. Dotman et al., Percept. Psychophys. 22, 109–122 (1977)]. Thus attempts to isolate the perceptually important cues to stop consonant identity should take into account the vowel context.