Contextual Tonal Variations in Vientiane Lao

Abstract

This study examines acoustic variations of lexical tones in Vientiane Lao under the influence of different tonal contexts. All 25 possible bitonal sequences from the five lexical tones in Lao are recorded, and their time course of fundamental frequency (F0) contours are measured. By examining the patterns of the F0 contours, this study explores the directionality and nature of contextual tonal variations in Lao: That is, it discusses whether Lao tones are more influenced by preceding tones (carryover effect) or by following tones (anticipatory effect) and whether these effects are assimilatory or dissimilatory. The results of this study indicate that the patterns of contextual tonal variation in Lao mostly agree with those in other tone languages. Carryover effects are greater in magnitude and extend farther into adjacent tones than anticipatory effects. Moreover, carryover effects are assimilatory: The onset of the F0 contour of a tone is raised when preceded by a tone with a high offset and lowered when preceded by a tone with a low offset. In contrast, anticipatory effects are mostly dissimilatory in nature: The F0 value of a tone is lowered when followed by a tone with a high F0 value somewhere in the contour and raised when preceded by a tone with a low F0 value somewhere in the contour.