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The Korean Association for the Study of English Language and Linguistics
[ Article ]
Korea Journal of English Language and Linguistics - Vol. 26, No. 0, pp.651-670
ISSN: 1598-1398 (Print) 2586-7474 (Online)
Print publication date 31 May 2026
Received 10 Mar 2026 Revised 28 Mar 2026 Accepted 20 Apr 2026
DOI: https://doi.org/10.15738/kjell.26..202605.651

Intra-Speaker Variability and Perceptual Sensitivity of English Vowels in Advanced Korean EFL Learners

Seyeon Choe ; Hyunkee Ahn
(First author) Ph.D. candidate, Department of English Language Education Seoul National University 1 Gwanak-ro, Gwanak-gu Seoul, Korea, Tel: +82-2-880-7670 caomei214@snu.ac.kr
(Corresponding author) Professor, Department of English Language Education Seoul National University, Tel: +82-2-880-7673 ahnhk@snu.ac.kr


© 2026 KASELL All rights reserved
This is an open-access article distributed under the terms of the Creative Commons License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The present study investigates Korean EFL learners’ intra-speaker variability and perceptual sensitivity in producing three American English vowel contrasts (/i–ɪ/, /ɛ–æ/, and /u–ʊ/). Thirty advanced Korean learners and eight native English speakers produced target vowels embedded in carrier phrases, and acoustic analyses were conducted using normalized Bark difference measures. Perceptual sensitivity was assessed using the A’ score to examine how perception relates to production variability. Paired-samples t-tests revealed no statistically significant differences in intra-speaker variability between new vowels (/ɪ, æ, ʊ/) and their corresponding similar vowels (/i, ɛ, u/) in vowel height. A significant difference was observed for the /i–ɪ/ contrast in vowel backness. Within the four-scenario framework of Smith et al. (2019), 81% of tokens fell into Scenario 1 (similar formants and similar variability) and 14% into Scenario 3 (different formants but similar variability), indicating that approximately 95% of productions showed native-like variability. Notably, the distribution of similar and new vowels across scenarios was the reverse of that reported by Smith et al. (2019), suggesting that learning environment (EFL vs. ESL) may modulate the formation of L2 phonetic categories predicted by the Speech Learning Model. Despite these production patterns, learners differed in perceptual sensitivity, and those sensitive to all three contrasts showed clearer separation among vowel categories than those who were not. These findings suggest that learners’ acoustic production patterns should be considered alongside perceptual sensitivity in characterizing L2 speech.

Keywords:

intra-speaker variability, perceptual sensitivity, American English vowel contrasts, acoustic analysis

Acknowledgments

An earlier version of this work was presented in the first author’s master’s thesis (Choe 2022) submitted to Seoul National University.

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