Data from about one hundred languages reveal that, in spite of resulting typically from articulatory reduction of peripheral vowels in unstressed position, full schwa may also occur in stressed position in stress languages and in unreduced syllables in languages lacking stress. Formant frequency data reveal that this vowel is mid central, though somewhat shifted to the mid back unrounded area (particularly if long and placed in open syllables and at the edges of words), and exhibits a higher or lower realization depending on the number of mid vowels in the vowel system. In spite of occurring in stressed position, full schwa resembles unstressed schwa in being very short, highly variable and possibly low intensity, which accounts for why it is prone to occur in closed syllables and longer words, and may receive stress only if the remaining vowel nuclei in the word are central and/or short peripheral. Moreover, variability in the F1 and F2 dimensions increases with the number of peripheral mid vowels, which appears to obey symmetry and dispersion principles of vowel space organization.

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.