Third International Conference on Spoken Language Processing (ICSLP 94)
This paper reports acoustic studies of vowel-to-vowel as well as consonant-to-vowel coarticulation effects on British English schwa in real-word sentences. The effects of both vocalic and consonantal contexts on F1 and F2 values of schwa are systematic. Different consonant contexts, in particular, introduce large variability in F2, covering a range of about 1000 Hz. The large variability was observed not only at the transitions but in the vowel midpoint. The extent of variability observed suggests that schwa is transparent in F2; its F2 values seem to be determined by the immediate consonant contexts plus the transconsonantal vocalic contexts. Thus schwa seems to be phonetically unspecified in F2 with no target value of its own apart from the value imposed by its contexts. On the other hand, variation in F1 was small and it was concluded that schwa is targeted in F1. That is, schwa is specified for [Height] but not for [Backness] in the traditional phonological terms.
Bibliographic reference. Kondo, Yuko (1994): "Phonetic underspecification in schwa", In ICSLP-1994, 311-314.