Identification and Discrimination of Phonemic Tones

Abstract

Measurements of the fundamental frequency patterns of many sets of tonally differentiated words yielded average curves for the five phonemic tones of Standard Thai (Siamese) on both short and long vowels. Experiments were then run to determine the role of fundamental frequency patterns in the perception of these tones. There were three major results: (1) Thai subjects easily identified tones in isolated monosyllables. (2) Highly intelligible tones could be synthesized on the Haskins Laboratories intonator with the average tonal contours that had emerged from the measurements. (3) When the five frequency contours were imposed synthetically on each of five utterances minimally distinguished by tone, the pitch contours overrode the effects of all other features observed in the stimuli. The overriding role of these contours opens the way to the study of discrimination at phoneme boundaries in the domain of prosodic features. The mid and high tones of Thai were chosen as a suitable pair for a start in this direction. These experiments had two results: (1) Shape difference is a stronger cue than pitch height for phonemic identification. (2) The hypothesis that there will be little or no sharpening of discrimination at this kind of phoneme boundary was supported or at least not contradicted.