Acoustic Analysis of the Production of Unstressed English Vowels by Early and Late Korean and Japanese Bilinguals

The production of unstressed vowels in English by early and late Korean- and Japanese-English bilinguals was investigated. All groups were nativelike in having a lower fundamental frequency for unstressed as opposed to stressed vowels. Both Korean groups made less of an intensity difference between unstressed and stressed vowels than the native speakers (NSs) of English as well as less of a difference in duration between the two types of vowel than the NSs. The Japanese speakers, whose native language has a phonemic length distinction, produced more nativelike durational patterns. Finally, the vowel quality (first and second formant frequencies) of unstressed vowels was different from the NS group's for the late bilinguals, for whom unstressed vowels were widely dispersed in the vowel space according to their orthographic representations, and from the early Korean bilinguals, who substituted the Korean high central vowel. The results are discussed in terms of the effect of the phonological status of first language phonetic features and age of acquisition.