The effect of emphatic stress on consonant vowel coarticulation
Lindblom, B., Agwuele, A.*, Sussman, H.* & Eir Cortes, E.
*Department of Linguistics, University of Texas, Austin, USA.
Journal of the Acoustical Society of America
This study assessed the acoustic effects of emphatic stress on [V1.CV2] sequences, when phrasal accent was applied to either V1 or V2, surrounding the voiced stops /b/, /d/, and /g/. The departure point was the realization that a confound exists when assessing overall degree of CV anticipatory coarticulation between (1) prosodically-induced variation, and (2) vowel context-induced variation. Three adult speakers each produced 360 tokens (six V1 contexts x 10 V2 contexts x three stops x two emphasis conditions). The analyses revealed two main stress-dependent effects: systematic differences in F2onset values and an expansion of vowel space. A modified locus equation regression metric was used to determine if the observed coarticulation patterns were linked to vowel space expansion, or reflected true coarticulatory change. The metric completely accounted for F2onset variations in /b/ tokens, but indicated F2onset values higher than expected for /d/ and /g/, especially when followed by back vowels. Formant calculations based on tube models indicated similarly increased F2onsets when stressed /d/ and /g/ were simulated with deeper occlusions resulting from more extensive closing movements. This result lends support to proposing that the stops of this study –like the vowels - were produced with less coarticulation under emphatic stress.