ABSTRACT

Pronunciation accuracy is a common challenge for EFL learners, especially in producing English vowel diphthongs, which often differ from sounds in their native language. These differences can cause phonological errors and reduce intelligibility in communication. This research analyzes the phonological errors made by sixth-semester students at Universitas Indo Global Mandiri in pronouncing English vowel diphthongs, identifies the most frequently mispronounced diphthongs, and examines whether students’ understanding of diphthongs is associated with their pronunciation accuracy. A descriptive qualitative approach was employed, using a pronunciation test and a questionnaire. Errors were categorized using the Surface Strategy Taxonomy: omission, addition, misformation, and misordering. Twenty-six students participated, and data were analyzed through phonetic transcription, descriptive statistics in Excel, and a Chi-Square test in SPSS. The results revealed 216 pronunciation errors out of 936 attempts (23.1%). Misformation was the most common error type (56.9%), followed by omission (40.7%) and addition (2.3%), with no misordering. The most problematic diphthongs were /əʊ/, /eɪ/, and /ɪə/, while /ɔɪ/ had the fewest errors. These findings suggest that misformation is the hardest to avoid and that certain diphthongs pose greater challenges. Although students may understand diphthongs theoretically, this does not ensure accurate pronunciation. Pronunciation instruction should emphasize articulation training and consistent practice rather than relying solely on theory.

Keywords: Phonological errors, Vowel diphthongs, Pronunciation accuracy, Surface Strategy Taxonomy.