Effects of Speech Rate on the Intelligibility of Non-Native Vowels

Abstract This paper examined the intelligibility of native and non-native vowel productions at three speech rates in native and L2 listeners. In Experiment I, native English speakers produced /i/-// in a Delayed Sentence Repetition Task at three speech rates (clear/citation/fast). The vowels were presented to 54 Catalan listeners in a forced-choice word identification task. The results revealed a significant main effect of vowel quality and speech rate, and a significant vowel quality x speech rate interaction (all ps<.001), indicating that Catalan listeners' identification accuracy was affected by speech rate and that they distinguished the vowels by means of duration. In Experiment II, vowel productions of Catalan speakers obtained in the same conditions as in Experiment I were presented to 6 native English listeners. Overall intelligibility decreased as speech rate increased. The results suggest that pronunciation and perceptual training for /i/-// at differing speech rates could be beneficial for Catalan EFL learners. Second language (L2) learners face several challenges when communicating in the foreign language. Whereas at the initial stages of language learning, speech processing demands and lexical search hinder effective communication, at more advanced stages as the L2 context expands, L2 users are faced with coping with speech variability in the input. On the one hand, they have to adapt to speaker variation, such a