Intelligibility of English Phonemes Spoken by L1 Japanese Speakers

This study explored which segmental sounds of English spoken by Japanese L1 speakers were intelligible to non-native speakers of English. It also investigated the reasons for the reduced intelligibility of some of the sounds. Thus, this study addressed two research questions: RQ1 “What English phonemes spoken with a Japanese accent are intelligible enough in international settings?”, and RQ2, “If some phonemes are not intelligible, what are the reasons?”. Four Japanese speakers participated in this study and they read aloud 23 sentences which included 13 target sounds /ɑː, ʊ, uː, æ, ʌ, f, v, θ, ð, sɪ, ʃ, l, r/. Then, the intelligibility of the four speakers was measured by a Cloze Transcription Task in which 12 non-native listeners transcribed the utterances. The results indicated that the consonants were more intelligible than the vowels. However, the intelligibility of the consonants /θ/ and /l/ were shown to be as low as the vowels. An error analysis conducted in order to find the reasons of reduced intelligibility indicated some major findings. First, the vowels tended to get misrecognized as other sounds more often than the consonants. Second, /æ/ and /ʌ/ were often mistaken for each other. Third, the consonants /r/ and /l/ were indistinguishable to a large extent. Next, error analysis revealed that the intelligibility of the consonants in the final position influenced the recognition of words. Therefore, clear articulation of the consonants in the final position is recommended for Japanese users of English. Lastly, a large portion of the misrecognitions occurred when the words were monosyllabic. From these results, this study proposes implications for teaching which it is hoped will be applied in schools in Japan.