Nasal coarticulation changes over time in Philadelphia English

This study examines change over time in coarticulatory vowel nasality in both real and apparent time in Philadelphia English. We measure nasal-adjacent vowels in words from a corpus of conversational speech and find systematic, community-level changes in degree of nasal coarticulation over time in Philadelphia. Specifically, in all speakers who were under the age of 25 when interviewed, there is an overall trend of increasing nasality in people born between 1950 and 1965, yet people born after 1965 move towards less nasality than speakers born earlier; finally, those born after 1980 reverse this change, moving again toward greater nasal coarticulation. This finding adds nasality to the set of phonetic dimensions that are demonstrably susceptible to diachronic change in a speech community. The observation that the degree of nasal coarticulation changes towards increased coarticulation at one time period and decreased coarticulation at a different time period adds to the growing body of evidence that subphonemic variation is not universally determined, suggesting instead that it is learned and encoded. Furthermore, the changes in nasality are independent from an observed frequency effect. These empirical patterns suggest that language-internal factors, such as lexical frequency, are independent from language external factors, such as community-level phonetic change over time. (C) 2014 Elsevier Ltd. All rights reserved.