The traditional Southern inflections associated with the Philadelphia regional accent are increasingly being displaced by Northern influences. A recent study supported by the National Science Foundation documents this trend through an analysis of Philadelphia neighborhood speech patterns over more than a century. The study, "A Hundred Years of Sound Change," to be published in the March 2013 issue of the scholarly journal Language, is authored by University of Pennsylvania linguists William Labov, Ingrid Rosenfelder and Josef Fruehwald.
Labov and his colleagues developed new computational methods for studying everyday speech to produce a view of continuous change in the Philadelphia dialect. The report finds two major patterns of change in the Philadelphia dialect, as part of a search for the causes of the language changes that have led to increasing differences among the regional dialects of North America.
The new methods for automatic measurement of the way vowels are pronounced were applied to yearly studies of Philadelphia neighborhoods since 1973. Nearly a million measurements show that two thirds of the Philadelphia vowels are involved in the process of change. In one instance, the vowel used in ate has steadily moved closer to the vowel of eat, as shown by the speaker's date of birth from 1888 to 1992. The change in progress affects equally people of all educational levels, both men and women. In contrast, the vowel of out and down has reversed direction, after moving toward a distinctively different Philadelphia sound for the first half of the century. For those born in the 1950s and later, this vowel moved progressively back towards the position it held in 1900.
The paper looks for an explanation of these differences in the relation of Philadelphia to its geographic neighbors. In the earlier period, many Philadelphia features resembled those found in Southern dialects, and these are the changes that have reversed direction. Those that have not are movements towards patterns heard in the Northern dialects of western New England, New York State and the Great Lakes Region. The "Northernization" of the Philadelphia region is related to other findings on the direction of linguistic change in North America. Local dialects are receding among younger speakers in the Southern States, while new sound changes are advancing steadily among younger speakers in the North.
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One hundred years of sound change in Philadelphia: linear incrementation, reversal, and reanalysis, Language, 2013.