Acoustic representations for tonal phonological categories.

Abstract

The learnability of tonal categories was investigated by studying how category separability is affected by different phonetic representations of tone. Gauthier et al. [(2007)] found that f 0 velocity contours densely sampled over time were sufficient for near-perfect categorization of Mandarin tones. Since infant learners begin as “citizens of the world” before developing language-specific representations of sound categories in response to ambient language input [Kuhl (2004)], cross-linguistic data were studied. Based on tonal production data from Bole, Igbo, Mandarin, Cantonese, and White Hmong, we found that (1) densely sampled f 0 velocity contours are insufficient for learning tones, but (2) coarse temporal sampling of phonetic features can produce well-separated tonal categories, and moreover, that (3) phonetic features for tonal representation necessarily extend beyond f 0 to voice quality features, and (4) features for tonal representation are language-specific. Results (2) and (3) were also supported by tonal perception experiments in Cantonese. It was found that listeners can maintain tonal identification accuracy under coarse sampling (down to three to five samples per syllable), with the speech signal interrupted with noise as in multiple phoneme restoration experiments. It was also found that listeners are biased in tonal identification by creaky voice in the speech signal.