The Interplay Between Segmental Timing and Coarticulation: Acoustic, Perceptual, and Phonological Investigations

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ABSTRACTBeddor 0118684With National Science Foundation support, Dr. Patrice Beddor will conduct three years of linguistic research on the variability of speech sounds. This project investigates how a particular kind of variability can eventually become a systematic property of a language, leading to language change. The focus is the overlapping articulation of adjacent or nearby sounds known as "coarticulation". In some sound changes, the sound that triggered the coarticulation is lost over time, leaving behind only its coarticulatory effects. For example, in French, Hindi, and hundreds of other languages, coarticulatory nasality in vowels was originally triggered only by a following nasal consonant, such as "m" or "n". But the nasal consonant dropped out over time, leaving vowel nasality as a systematic and now required property of the word. Dr. Beddor hypothesizes that the loss of a coarticulatory trigger and the linking of its properties to another sound involve a stage in which shortened duration of the trigger is offset by more extensive coarticulatory influences (e.g., nasal consonants shorten as nearby vowels become more nasal). She further hypothesizes that listeners facilitate these changes by being perceptually insensitive to variation in such timing relationships. Dr. Beddor's research mimics the stages of a language's change by studying four languages that differ in the relevant timing patterns: English, Thai, Greek, and Ikalanga. Acoustic analyses of these languages will be conducted to verify the timing patterns that emerged in preliminary studies. These analyses will be followed by perceptual testing and further phonological investigations.This multi-language research has theoretical and practical significance across domains affected by speech science. First, it will broaden the empirical database on which theories of sound change, speech production, and speech perception are grounded. Second, better understanding of speech variation and speech sound change reveals how some dialect differences emerge. Better understanding of dialect emergence may reduce the social stigmatization attached to some speech varieties. Third, the perceptual tests that explore listener sensitivity to speech variation have implications for theories of how infants extract phonetic regularities in the languages they are learning. Finally, these results will bear on speech technology. Computer speech recognition systems make more errors than humans do. This is partly because computer recognizers display greater sensitivity to coarticulatory variation. Study of the kinds of speech variability that human listeners are sensitive to may help solve this practical challenge in speech engineering.