Durations of American English vowels by native and non-native speakers: acoustic analyses and perceptual effects.

The goal of this study was to examine durations of American English vowels produced by English-, Chinese-, and Korean-native speakers and the effects of vowel duration on vowel intelligibility. Twelve American English vowels were recorded in the /hVd/ phonetic context by native speakers and non-native speakers. The English vowel duration patterns as a function of vowel produced by non-native speakers were generally similar to those produced by native speakers. These results imply that using duration differences across vowels may be an important strategy for non-native speakers' production before they are able to employ spectral cues to produce and perceive English speech sounds. In the intelligibility experiment, vowels were selected from 10 native and non-native speakers and vowel durations were equalized at 170 ms. Intelligibility of vowels with original and equalized durations was evaluated by American English native listeners. Results suggested that vowel intelligibility of native and non-native speakers degraded slightly by 3-8% when durations were equalized, indicating that vowel duration plays a minor role in vowel intelligibility.