A Spectrographic Study of Allophones of Voiceless Stop Consonants in American English

Abstract

The times of closure and aspiration in /p,t,k/ were investigated using spectrograms of naturally read texts. Most obvious effects in the data are the differences between word-initial and word-final stops and between stressed-syllable-initial and unstressed stops. There are several effects of phonetic environment—notably a shortening of closure time when the stop is preceded by a nasal. Word-initial stops form a class with closure and aspiration times varying proportionately from short duration in function words to long durations for emphatic and prepausal content words with primary stress on initial syllables. Final stops form a class tending toward either long closure times or long aspirations, but not both, depending on the immediate phonetic context. Inside the word, the stops form more tightly grouped classes, dependent on the lexical stress and phonetic environment. In general, the durations of closure and aspiration of the voiceless stops are predictable from the identity of the consonant and from its phonological context.