Acoustic correlates of English glottal [t] allophone

Abstract

This experiment investigates the acoustics of American English coda [t], which is often glottalized. A list of monosyllabic and bisyllabic words with matching vowel quality in target syllables across pairs was devised. The matching pairs were controlled for lexical frequency from the celex database. The words were read in isolation and in a frame sentence, where the target word was at the end of an intonational phrase. Results show that there is glottalization on the vowel preceding [t], which is interpreted as laryngeal coarticulation from the glottal allophone of [t]. Additionally, results show that for some speakers the proportion of the vowel that is glottalized is longer in sentences than in isolated words. Results of a cepstral measure of harmonics-to-noise-ratio (Hillenbrand et al., 1994) are different from what was found for Ju–hoansi glottalized consonants (Miller-Ockhuizen, 2002), but similar to results for glottalized vowels. That is, Gamnitude of R1 increased toward the end of the vowel. Since glottalization, as measured via a low H1–H2 (NiChasaide and Gobl, 1997) and aperiodicity seen through waveform inspection, does occur on the vowel, this suggests an articulatory mechanism for glottalization different from constriction of the glottis, such as false vocal-fold contraction (Fujimura and Sawashima, 1971).