An investigation of lingual coarticulation resistance using ultrasound

Introduction This paper uses ultrasound data in order to explore the extent to which lingual coarticulatory resistance for front lingual consonants and vowels in VCV sequences increases with the place and manner of articulation requirements involved in their production. Coarticulatory resistance for a given consonant or vowel is a measure of its degree of articulatory variability as a function of phonetic context such that the less the target segment adapts to the articulatory configuration for the flanking segments, the more coarticulation resistant it may be assumed to be. In principle, ultrasound should be more appropriate than EPG and EMA for studying coarticulatory resistance since it allows us to measure phonetic contextual effects not only at the alveolar and palatal zones but at the velar zone and at the pharynx as well. In the present investigation coarticulatory resistance will be evaluated for the Catalan consonants /t, d, n, l, s, ɾ, r, ʎ, ɲ, ʃ/ and vowels /i, e, a, o, u/ embedded in symmetrical VCV sequences. In present-day Catalan, those consonants may be characterized as follows: /t, d/ are dentoalveolar and /d/ is realized as an approximant intervocalically ([]); among the alveolar consonants /n, l, s, ɾ, r/, /ɾ/ is a tap, /r/ is a trill and /l/ is clear rather than dark (as for the Catalan speakers who took part in the present study, F2 for /l/ amounts to 1400 Hz next to /i, e/ in the case of males and to 2500 Hz next to /i/ and 1700 Hz next to /e/ in the case of females); /ʃ/ is palatoalveolar and /ʎ, ɲ/ are alveolopalatal. Within the framework of the degree of articulatory constraint (DAC) model of coarticulation and in line with kinematic data reported elsewhere (Recasens & Espinosa, 2009), we hypothesized that the degree of coarticulatory resistance for the phonetic sounds under investigation ought to conform to specific trends. On the one hand, palatal consonants and palatal vowels were expected to be most resistant since their production involves the entire tongue body. On the other hand, coarticulatory resistance for dentoalveolar consonants should depend on manner of articulation and thus, be highest for /s/ and the trill /r/, lowest for the approximant [], and intermediate for /t, n, ɾ/ and clear /l/. As for vowels, differences in tongue constriction location and lip rounding should render /a/ less variable than /o, u/. In sum, our initial hypothesis was that coarticulatory resistance ought to decrease in the progression /ʎ, ɲ, ʃ/ > /t, n, ɾ, l/ > /s, r/ > /d/ for consonants and /i, e/ > /a/ > /o, u/ for vowels.