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Abstract
The effects of vowel height, tense/lax distinction in vowels, position in utterance, and post-vocalic consonant voicing and manner of articulation on vowel duration were studied. It was demonstrated that the incompressibility model (Klatt, 1973, 1979) did not predict the observed durations as well as a linear regression based model, which was also rejected.
Further analysis revealed that vowel height could be modeled as an additive effect, although there were some speaker-specific exceptions. The influence of position in utterance was additive when the post-vocalic consonant was voiceless. The effects of post-vocalic consonant voicing and position in utterance when the post-vocalic consonant was voiced, were not additive and were modeled well as multiplicative process. Position in utterance exhibited an additive component as well. Voiceless post-vocalic fricatives had an additive lengthening effect on vowels. When very long, particularly before final voiced fricatives, the durations of tense vowels and diphthongs appeared to be subject to a process of saturation: they were shorter than expected from the mean lax vowel duration. Although the saturation of vowel durations obscured the underlying mode by which voiced fricatives affected the duration of preceding vowels, there were indications that voicing had a multiplicative effect and manner an additive effect. An analysis of published data tended to corroborate these conclusions.
Of particular interest among these results is the dependency of the form of the model of position in utterance effects on post-vocalic consonant voicing. The multiplicative component of the position effect before voiced consonants is reinterpreted as reflecting an increase of the voicing factor in final position. Final lengthening then consists of a relatively small additive increment; voicing acts multiplicatively. It is hypothesized that multiplicative processes are phonemic and additive ones largely unintentional by-products of the mechanism of speech production.
