Perception of Thai tones in citation form and connected speech

Abstract

F0 contour shapes of the five tones of Thai differ from citation form to connected speech [Potisuk et al., Phonetica 54, 2242 (1997)]. ‘‘Falling’’ tones have a rise-fall contour in citation, but may be realized as a rise in fluent speech. This study investigates whether Thai listeners can reliably distinguish tones in connected speech, and whether any cues to tone identity remain stable across contexts. In four experiments, ten Thai listeners identified naturally produced and digitally altered tones in a forced-choice task. In experiment one, listeners identified naturally produced ‘‘falling’’ tones with 100% accuracy in citation forms and 96% accuracy in sentences, despite differing contours. In experiments 2–4 (replicating and extending Abramson [Lg&Sp 21, 319325 (1978)]), F0 onset and offset, peak height, and peak alignment were systematically modified on syllables in citation and sentence contexts. In all contexts, tones identified as high or low had an F0 peak or valley aligned to the right edge of the syllable. Mid tones had no F0 inflection. Tones identified as falling or rising necessarily had a pitch inflection at the syllable midpoint (end of the first mora). These findings support the view that tones are aligned with moras in Thai.