The influence of phonetic context on the acoustical properties of stops

Abstract

In American English, stop consonants may be released, unreleased, or deleted (e.g., the phoneme /t/ in “tea,” “basketball,” and “softly,” respectively). The particular acoustical realization is almost obligatory in some environments and highly variable in others. The purpose of our study was to quantify the influence of context, including syllable structure, on the acoustical properties of stop consonants. Or database consisted of some 5200 stops collected from 1000 sentences. Phonemic transcriptions, including lexical stress and syllable markers, were provided and aligned with the speech waveforms. The stops were grouped into categories corresponding to their position within syllables (e.g., syllable‐initial‐singleton, syllable‐final‐affix, etc.) and marked according to their local phonemic context. Segment durations were measured and the stops were classified as released, unreleased, or deleted on the basis of their duration and voice onset time (VOT). In the analysis of these data, including the examination of VOT and other durational measurements, we found substantial effects of both syllable structure and phonemic context. For example, over 98% of the stops in syllable‐initial position are released, regardless of the preceding phoneme. Syllable‐final singleton stops are released 65% of the time when followed by a vowel (as in “oak is”), and unreleased 73% of the time when followed by a consonant (as in “sickness”). A stop is most likely to be deleted (over 40% of the time) when it is the last member of a syllable‐final cluster containing an obstruent and followed by a syllable‐initial consonant (as in “mostly”). An /s/ preceding a stop consonant or a semivowel following, has a stronger influence on its VOT if it appears within the same syllable. Similarly, a singleton stop's voicing characteristic affects the duration of a preceding vowel differently, depending on whether the two segments are in the same syllable. Detailed results will be presented at the meeting. [Work supported by an AT&T Bell Laboratories Cooperative Research Fellowship and by DARPA.]