Variation in stop releases in American English spontaneous speech.

This study extends previous examinations of pre-consonantal stop releases in American English by investigating spontaneous speech from the National Public Radio’s StoryCorps project. Previous research has shown that in read speech, English speakers do not release stops in pre-stop and pre-pausal environments between 50 and 60% of the time. In spontaneous speech from more than 10 speakers, stops before obstruents and nasals in word-internal position (e.g., doctor, act), across a word boundary (e.g., pack these), or at the end of a phrase are produced without an acoustic release 62% of the time, while 29% of stops are released and 8% are deleted altogether. The only position in which there are more released stops than unreleased ones is in pre-pausal position (59.2% vs 38.8%). Deletion only occurs for coronals /t/ and /d/, which constitute 75% of the stops in the corpus. Stops are most likely to be unreleased before other stops (86%); before fricatives they are divided between being unreleased (53.7%), released (25.4%), and deleted (20.9%). The status of stop releases in English will be discussed with respect to articulatory coordination, aerodynamics, and stylistic uses by individual speakers. [Research supported by NSF.]