Duration of American English vowels and its effects on intelligibility for native and non-native speakers

Abstract

Durations of 12 American English vowels were measured for English-, Chinese-, and Korean-native speakers. Results showed that vowel duration was significantly affected by speaker groups. That is, vowels produced by English- and Korean-native speakers were significantly longer than vowels produced by Chinese-native speakers. The patterns of vowel duration as a function of vowel category were quite similar between native and non-native speakers. However, Mandarin Chinese vowels did not differ in duration across Chinese-native speakers, while durations of Korean vowels were significantly different across Korean-native speakers. These results suggest that non-native speakers were able to follow the duration pattern of native speakers in their vowel production. When vowel duration was equalized across vowel category with the central vowel nucleus remained, vowel intelligibility significantly dropped about 5% compared to vowels presented in the syllabic context for native and non-native speakers. The perceptual effects of vowel duration on vowel intelligibility appeared to be the same for native and non-native speakers, independent of speaker language background and the second language proficiency level.