The impact of variation in phoneme category structure on consonant intelligibility

Newman et al. [J. Acoustic. Soc. Am, 109, 1181-1196 (2001)] suggested that phoneme identification accuracy and speed for a given talker was affected by the degree of variability in their production of phoneme categories. This study investigates how intra-talker variability in the production of two phoneme contrasts varies with age and gender, and how this variability affects perception. Multiple iterations of tokens differing in initial consonants (/s/-/ʃ/, /p/-/b/) were collected via picture elicitation from 40 adults and 31 children aged 11 to 14; measures of within-category dispersion, between-category distance, overlap and discriminability were obtained. While females produced more discriminable categories than males, children produced farther yet more dispersed - and thus similarly discriminable - categories than adults. Variability was contrast-specific rather than a general talker characteristic. Tokens with initial /s/-/ʃ/ from pairs of adult and child talkers varying in between-category distance or overlap were presented for identification. The presence of overlap had a greater effect on identification accuracy and speed than between-category distance, with strongest effects for adult speakers, but reaction time correlated most highly with within category dispersion. These data suggest that talkers who are less consistent in their speech production may be perceived less clearly than more internally-consistent talkers