Perception of English High Vowels : Duration as a Cue by Korean Speakers of English

This study examines the acoustic characteristics of English high tense and lax vowels (/i, I, u, ʊ/) and the perceptual difference of those vowels between English speakers and Korean speakers of English. In Experiment I, the first three formant values and duration of the four vowels in /hVd/ carrier were measured. The result shows that the high tense vowels have larger F2–F1 values and longer durations than high lax vowels. In Experiment II, each word’s vowel duration was manipulated into the range from 170ms to 290ms in 30ms increments. Two English speakers and six Korean speakers of English were asked to listen to a pair of tense and lax vowel words (e.g., heed_230ms–hid_170ms for the front vowel test and hood_290ms –who’d_200ms for the back vowel test), and to discriminate the pair by choosing one of the options either heed-hid or hidheed for front vowels and either who’d-hood or hood-who’d for back vowels. The results demonstrate that English speakers discriminated tense vowels from lax vowels 100% correctly regardless of the different durations, compared to 62% accuracy rate in Korean speakers of English. Most errors were found when the duration of lax vowels was lengthened and the duration of tense vowels was shortened. Therefore, the results of this study demonstrate that Korean speakers mainly rely on vowel duration as a cue to discriminate the tense and lax vowels. The pedagogical implications of this phenomenon will be discussed.