Static and Dynamic Acoustic Cues in Distinctive Tones

It is conventional to classify phonemic tones into dynamic or contour tones and static or level tones. The perceptual relevance of this impressionistic dichotomy is considered here for Central Thai, which has two dynamic tones (falling and rising pitches) and three static tones (high, mid, and low). A fundamental-frequency range appropriate to an adult male voice was used to synthesize three series of tonal variants on a syllable type available for five tonally differentiated words: (1) 16 F o levels at intervals of 4 Hz, (2) 16 F o movements from a mid origin to end points ranging from top to bottom of the range in steps of 4 Hz, and (3) 17 variants rising from the bottom to end points from top to bottom in steps of 4 Hz. The stimuli were played to native speakers for identification. The results indicate that level variants contain sufficient cues for identification as static tones but with considerable overlap. Identification, however, is enhanced by slow F o movement. Rapid F o movement is required for dynamic tones. Although imprecise, the typological dichotomy is useful.