Vowel Space Characteristics of English Monophthongs and Diphthongs Produced by Male and Female Korean Learners of English

Abstract

The phonetic realization of English nine monophthongs /i, ɪ, ɛ, æ, ʌ, ɑ, ɔ, ʊ, u/ and five diphthongs /aɪ, aʊ, eɪ, oʊ, ɔɪ/ were investigated in the production data of Korean male and female learners of English. The speech material was composed of one syllable words with target monophthongs and diphthongs such as ‘beat’ and ‘bite’. The first and second formant frequency values were calculated at the mid-point for monophthongs and at onset and offset of diphthongs. The vowel space positions of diphthong onsets and offsets were examined in relation with the positions of nearby monophthongs. The female data and male data were presented separately because of gender variation of formant structure. The nonnative formant patterns were compared with previous relevant studies of native speech data for English monophthongs and diphthongs. The speech data of Korean learners of English shows proximity of monophthongs /i, ɪ/, /u, ʊ/, and /ɛ, æ/ in the vowel space. The back vowels /ɔ, ʊ, u/ are close to each other in vowel space. The study results show that the onset and offset of diphthongs are fairly close to the relevant monophthongs, which is not the case for native English speakers in previous studies. In addition, the study results suggest that Korean learners of English might have some difficulties in producing English diphthongs with their offsets in the back position such as /aʊ, oʊ/. The study results concerning nonnative distribution of monophthongs and diphthongs in vowel space were discussed as having implication for improving the acquisition process of L2 English vowel system.