Ultrasound and center of gravity frequency data for the sequences /ʃ#s/ and /s#ʃ/ produced by Central Catalan speakers reveal that the former sequence is implemented through continuous articulatory and spectral trajectories which, depending on speaker, may be: intermediate between /ʃ/ and /s/ all throughout, thus supporting a dynamic blending mechanism; /ʃ/-like at onset and intermediate between the two fricatives at offset, which is indicative of C1-to-C2 carryover coarticulation. The sequence /s#ʃ/, on the other hand, undergoes regressive assimilation into [ʃ(ʃ)] according to the acoustic signal but less clearly so in the light of the articulatory data. This discrepancy appears to be due to the fact that, while C1=/s/ assimilates indeed to C2=/ʃ/ at constriction location, coarticulation-induced changes in tongue body configuration behind the primary articulator may occur as long as they do not jeopardize the front-cavity dependent frequency characteristics of the [ʃ] frication noise. Differences in articulatory complexity between /ʃ#s/ and /s#ʃ/ appear to result from the production mechanisms involved, i.e., tongue dorsum raising behind the /s/ constriction for /s#ʃ/ and tongue body repositioning for /ʃ#s/. In agreement with this interpretation, /ʃ#s/ but not /s#ʃ/ turned out to be longer than /s#s/ and /ʃ#ʃ/.

The present study is concerned with some aspects of the production of [ɨ] and [ə] in Romanian, i.e., their position within the vowel space, degree of acoustic variability and acoustic duration. To this end, acoustic data were collected for the Romanian stressed vowels [i e a o u ɨ ə] produced by six speakers in controlled consonantal context conditions and real and nonsense words. The formant frequency data reveal that [ɨ] and [ə] do not overlap along the F1 dimension, which may be ascribed to the need to set in contrast the two central vowels phonologically. Moreover, [ɨ] is clearly more variable in F2, and thus in vowel fronting, than schwa. Regarding segmental duration, [ɨ] is as short as high vowels and shorter than schwa, whose duration is comparable to that of mid vowels. The phonetic characteristics for stressed schwa in Romanian are in contrast with those for the same vowel in other world’s languages, in which it is highly variable and shorter than all or most peripheral vowels. This behaviour may be attributed to the existence of two central vowels, while suggesting that [ə] has a well-defined articulatory target in the Romanian language.