Speech Rate and English Vowel Reduction

Abstract

The present study examines the relation between phonetic vowel reduction and speech rate in English sentences spoken by native speakers and Korean speakers. This study specifically focused on six vowels (/i, u, ɛ, æ, ɑ, ɔ/). Twenty-six native female speakers and forty Korean female speakers read six sentences which included these vowels, at normal and fast speech rates. Individual vowels moved inward forward the formant centroid as the speech rate increased, and as a result, the size of the vowel space was reduced from normal to fast speech rates. The results indicated that the increase of speech rate caused the formant target undershoot by the effects of the time reduction rather than the increased articulatory velocity, or the increase in the extent of coarticulatory overlapping between the consonant and a following vowel, and stress did not affect the formant target undershoot.