How consonants, dialect and speech rate affect vowel devoicing?

We examined the glottal opening pattern during devoicing environment in Japanese, with respect to the factors that facilitate or suppress devoicing. The factors include consonantal environment, dialects, speech rate, consecutive devoicing environment and phrase final position. The results indicated that glottal opening patterns are twofold: a single phaseand 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. Voicing of vowels in the environment of /h/ is due to the tendency for /h/ to be voiced in Japanese. 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. Greater interpersonal variations appeared for devoicing at phrase final position.