Comparing stress, lexical focus, and segmental focus: patterns of variation in Arabic vowel duration

This paper reports a study of how stress and two types of focus affect the durational correlates of phonemic contrasts. Specifically, it examines how vowel durations and formants are affected by quantity differences and by the voicing on a following obstruent, when the vowels are in stressed or unstressed syllables, when the word is focused, as well as when it is the subject of explicit segmental focus contrasting it with another member of a minimal pair. Results find both a quantity and a voicing effect on vowel durations, though these two effects differ as to how they interact with stress and focus. Quantity effects are increased by stress and segmental focus, while voicing effects are generally unaffected by stress and focus, suggesting that voicing effects are not phonemically specified, while quantity differences are. Stress increases durations and reduces undershoot in addition to increasing the amount of quantity contrast. Lexical focus generally has the effect of increasing F1, and segmental focus on quantity contrasts increases differences in duration, while segmental focus on voicing increases vowel durations in general. Both kinds of focus are less consistent across speakers than is stress. These results are discussed with respect to how speech behavior is conventionalized with respect to a linguistic code. (C) 2002 Elsevier Science Ltd.