The effects of cross-generational and cross-dialectal variation on vowel identification and classification

Cross-generational and cross-dialectal variation in vowels among speakers of American English was examined in terms of vowel identification by listeners and vowel classification using pattern recognition. Listeners from Western North Carolina and Southeastern Wisconsin identified 12 vowel categories produced by 120 speakers stratified by age (old adults, young adults, and children), gender, and dialect. The vowels /ɝ, o, ʊ, u/ were well identified by both groups of listeners. The majority of confusions were for the front /i, ɪ, e, ɛ, æ/, the low back /ɑ, ɔ/ and the monophthongal North Carolina /aɪ/. For selected vowels, generational differences in acoustic vowel characteristics were perceptually salient, suggesting listeners' responsiveness to sound change. Female exemplars and native-dialect variants produced higher identification rates. Linear discriminant analyses which examined dialect and generational classification accuracy showed that sampling the formant pattern at vowel midpoint only is insufficient to separate the vowels. Two sample points near onset and offset provided enough information for successful classification. The models trained on one dialect classified the vowels from the other dialect with much lower accuracy. The results strongly support the importance of dynamic information in accurate classification of cross-generational and cross-dialectal variations.