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Articulatory correlates of stress

To make the stressed syllable stand out from its neighbours, it is produced with greater physiological effort on the part of the speaker than its unstressed counterparts.


To make the stressed syllable stand out from its neighbours, it is produced with greater physiological effort on the part of the speaker than its unstressed counterparts (e.g. Ladefoged 1967). The greater effort will be exerted at any stage in the speech production process, i.e., by the subglottal mechanism (more air is pushed out of the lungs), by the glottal (laryngeal) system (contraction of laryngeal muscles, generating a change in pitch) and by the supraglottal organs (e.g. larger and faster displacement of lips, tongue and jaw, yielding more clearly articulated vowels and consonants). The greater effort is seen, first of all, in closer approximation of articulatory target configurations for segments in stressed syllables. More extreme articulatory movements require more time than small displacements of the vocal organs. The result of this is that segments in stressed syllables have longer durations – all else being equal – than unstressed segments (see also Extra below). Moreover, in terms of the theory of articulatory phonology (e.g. Browman and Goldstein 1992), there is relatively little overlap between adjacent segments in a stressed syllable. In contradistinction to this, unstressed segments greatly overlap, which leads to considerable reduction of segmental contrast. This also accounts elegantly for the observation that segments at the edges of stressed syllables tend to maintain their identity (resist coarticulation with an adjacent segment in an unstressed syllable) whilst unstressed segments across the syllable boundary are disproportionally affected by coarticulation (e.g. Dogil 1999; see also Extra below).

Effort expended at the laryngeal level of speech production takes the form of contracting selected muscles that influence the speed with which the vocal folds vibrate during phonation. The result may be a rapid increase (through activation of cricohyroid and vocalis muscles) or decrease (through activation of the sternohyoid muscle) of the repetition rate of the glottal cycle, causing, respectively, a rise and fall of vocal pitch. A secondary effect of laryngeal effort may be a tightening of the vocal folds (mm. vocales), which will then snap together more forcefully than when in a less tightened state. Finally, increased effort at the subglottal level will push more air per unit time through the glottis, causing, first of all, an increase in intensity of the sound produced by the glottal siren. Secondarily, the greater volume-velocity of the airstream through the glottis boosts the Bernoulli suction effect. The increased suction and the tightening of the vocalis muscles conspire to shorten the closing phase of the glottal cycle, which causes the spectrum to become flatter, boosting the intensity of higher harmonics, thereby generating a louder sound.

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The view on the relationship between expansion of the articulatory space and duration goes back to Lindblom (1963). Given that longer duration is not associated with clear articulation in phrase-final syllables (domain-final lengthening), it seems reasonable to assume that clarity of articulation is the primary goal which is subserved by lengthening in stressed syllables.

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The coarticulation window of a stressed vowel may extend to an unstressed neutral vowel schwa in the preceding syllable, across an intervening consonant, and yield both acoustic and perceptual effects (e.g. Van Heuven and Dupuis 1991).

  • Browman, C. P. & Goldstein, L1992Articulatory Phonology: An overviewPhonetica49155-180
  • Dogil, G1999The phonetic manifestation of word stress in Lithuanian, Polish, German, and SpanishWord prosodic systems in the languages of EuropeBerlinde Gruyter
  • Heuven, Vincent J. van & Dupuis, M. Ch1991Perception of anticipatory VCV coarticulation: effects of vowel context and accent distributionProceedings of the 12th International Congress of Phonetic SciencesAix en Provence78-81
  • Ladefoged, Peter1967Three areas of experimental phonetics: stress and respiratory activity, the nature of vowel quality, units in the perception and production of speechLondonOxford University Press
  • Lindblom, B. E. F1963Spectrographic study of vowel reductionJournal of the Acoustical Society of America351773-1781