Spectrographic Study of Vowel Reduction

Our knowledge of the acoustic nature of reduced vowels as found in rapid speech or short syllables appears to be rather limited. It is generally assumed that a vowel that is shortened, e.g., owing to its occurrence in a weakly stressed syllable, tends to approach ə both articulatorily and perceptually. This paper reports some of the results that have emerged from a spectrographic study of vowel reduction in Swedish. The speech material consisted basically of 24 nonsense words formed by commutation of /ɪ, ɛ, ʏ, œ, a, θ, ɔ, ʊ/ in three consonantal environments /b-b/, /d-d/, and /g-g/. Preliminary experimentation preceded the selection of sentence frames that generated durations of the above vowels within 100–300 msec. The results indicate continuous shifts in formant frequencies as a function of vowel duration. As the vowel grows shorter, this shift, which is most conspicuous in the second formant, takes the form of an increasing displacement away from a hypothetical “bull's-eye” formant frequency and is directed towards the adjacent consonant locus. The magnitude of the displacement seems to be dependent on the distance in frequency between the vowel target and the locus. The results are interpreted as indicative of constraints inherent in the articulatory mechanism.