We report the results of a comprehensive dialectal survey of three vowel duration phenomena in North American English: gross duration differences between dialects, the effect of post-vocalic consonant voicing, and intrinsic vowel duration. Duration data, from HMM-based forced alignment of phones in the Atlas of North American English corpus , showed that 1) the post-vocalic voicing effect appears in every dialect region and all but one dialect, and 2) dialectal variation in first formant frequency appears to be independent of intrinsic vowel duration. This second result adds evidence that intrinsic vowel durations are targets stored in the grammar and do not result from physiological constraints.
Bibliographic reference. Tauberer, Joshua / Evanini, Keelan (2009): "Intrinsic vowel duration and the post-vocalic voicing effect: some evidence from dialects of north american English", In INTERSPEECH-2009, 2211-2214.