15th International Congress of Phonetic Sciences (ICPhS-15)
Realization of coda /t/ in American English is sensitive to segmental and prosodic context, as well as speaker age. One 20 year old and three 50 year old American women read an extensive word list designed to pinpoint some effects of context. For the older women, preceding low vowels conditioned more glottalization of /t/, presumably because of the greater effort involved in making an oral closure from a low tongue position. Even intervocalically, the four speakers produced some glottal /t/s, where flapping would be expected. The older speakers nearly always glottalized /t/ preceding /p, t, m, n, l, r, w, j/ and sometimes before /k, f, ʘ, s/. Segmental conditioning was practically irrelevant to the younger speaker who dependably released coda /t/ only utterance-finally. For her, the glottal variant is common enough that the flap is in danger of being replaced as the basic intervocalic allophone.
Bibliographic reference. Lavoie, Lisa M. (2003): "Coda /t/ glottalization in 20 & 50 year old American women", In ICPhS-15, 2797-2800.