We examined the glottal opening pattern during devoicing environment,with respect to the factors that facilitate or suppress devoicing. The results indicated that glottal opening patterns are twofold: a single phase- and a double phase opening for /CVC/. Only single phase openings appeared at typical consonantal environments for a Tokyo speaker. Gestural reorganization is assumed for these cases. Double phase opening appeared for an atypical consonantal environment for the Tokyo speaker. For a speaker of Osaka dialect, in which devoicing is less frequent, double phase opening appeared regardless of a typical or atypical consonantal environment. The effect of atypical consonantal environments and dialect on devoicing are due to glottal gesture overlap. In faster speech, a double phase tends to merge which facilitates devoicing. In consecutive devoicing environments, the vowel in a typical consonantal environment is the first candidate with/without devoicing of the following vowel. The following vowel can be devoiced if the glottal opening for the preceding /CVC/ is reorganized. During the phrase final /u/, both single- and double phase openings appeared for Tokyo speakers. Greater interpersonal variations appeared for devoicing at phrase final position.

Index Terms: vowel devoicing, consonantal environment, speech rate, dialects, phrase final position, consecutive devoicing environments