An Exploratory ultrasound study of unreleased plosive consonant sequence in Cantonese

A plosive consonant in Cantonese is phonetically unreleased in the coda, but it is released in the onset. The acoustic characteristics of the plosive-plosive consonant sequence resembles a singleton stop, leading to a potential difficulty in differentiating the former from the latter. A recent study by Ghosh and Narayanan (2009) showed that closure duration could be used to distinguish incomplete stops in a stop-stop sequence from a singleton stop in American English, possibly attributable to assimilation and coarticulation. This raises the question whether places of articulation will be maintained in the unreleased coda in Cantonese. This study examined the acoustic and articulatory characteristics of the unreleased stop in the hetero-syllabic consonant sequence. A production experiment using ultrasound was conducted on two subjects who took part in a reading aloud task. Target words/characters containing the test stops /t/ or /k/ were combined with other words beginning with either /p/, /t/ or /k/ to generate various homorganic and heterorganic stop-stop sequences. Closure duration of the onset plosive was found significantly shorter than that of the hetero-syllabic stop-stop sequence, but closure duration did not differ across places of articulation. The preliminary analysis of the ultrasound data of one speaker also indicates articulatory anticipation.