Dialectal variation study published in JASA
A paper by Assistant Professor Jason Shaw, in collaboration with Arwen Blackwood Ximenes and Christopher Carignan of Western Sydney University, has been published in a special issue of the Journal of the Acoustical Society of America (JASA).
The paper, entitled A comparison of acoustic and articulatory methods for analyzing vowel differences across dialects: Data from American and Australian English, discusses various methods by which phoneticians study how speech sounds are pronounced. Currently, researchers often try to deduce the motion of the mouth during the pronunciation of a word by examining the sound wave emitted from the voice. This is done by decomposing the wave into a collection of simpler waves, each with a different frequency. Due to the shape of the vocal tract and the mouth, some of these frequencies are amplified; these frequencies are known as formants.
Jason’s study investigates the two lowest formants: F1 and F2. It has long been known that during a vowel, F1 and F2 indicate the position of the tongue in the mouth—the lower the F1, the closer the tongue is to the roof the the mouth, and the lower the F2, the closer the tongue is to the back of the mouth. Because of this, linguists often use F1 and F2 to deduce the position of the tongue when pronouncing vowels. Jason’s study, however, shows that F1 and F2 do not always accurately reflect the position of the tongue. By recording the tongue movements of five North American English speakers and four Australian English speakers, the researchers found that other movements of the mouth, such as rounding the lip and curving the tongue, can also have effects on F1 and F2. Based on these findings, the paper constructs a richer comparison of North American and Australian English in terms of their vowels by taking into consideration other factors that might affect F1 and F2.
The paper was published in July 2017, and is available on the JASA website. The paper is part of the Special Issue on Advancing Methods for Analyzing Dialect Variation, a collection of papers seeking to improve the techniques by which linguists compare various dialects of a language.