The mechanisms of vowel epenthesis in non-native consonant clusters

We investigated the mechanisms of vowel epenthesis in consonant clusters using the WAVE system (NDI Corp.). Tongue tip movements were measured during the articulation of native and non-native consonant clusters in English. The subjects were three English speakers (2 males and 1 female). The speech samples were 3 words: blat, bnat, btat. In these words, consonant cluster /bl/ is native in English, but /bn/ and /bt/ are non-native consonant clusters in English. All these second consonants, /l, n, t/ are articulated with tongue tip placed behind alveolar ridge. These words were embedded in a carrier sentence, “Say X.”, and these sentences were uttered 10 times each in random order. We decided epenthetic vowels from visual inspection of spectrograms and wave forms. In native consonant cluster /bl/, there were 3 epenthetic vowels in utterances (10%), but in non-native consonant clusters, /bn/ and /bt/, there were epenthetic vowels in 66.7% and 33.3% of utterances, respectively. Tongue tip displacement from first consonant /b/ to second consonant /n, l, t/ was measured. The normalized mean tongue tip displacement of /bl/, /bn/, and /bt/ was 0.26, 0.36, and 0.41, respectively. Two-way ANOVA (Speaker vs. Cluster) showed significant interaction (p=0.0002), and significant main effects in Speaker (p<0.0001) and Cluster (p=0.0020). These results suggested that in native consonant clusters, first and second consonants are strongly combined, while in non-native consonant clusters, they are not combined. Vowel epenthesis would result from this weak coupling between consonants.