Acoustic modeling of American English vertical bar r vertical bar

Recent advances in physiological data collection methods have made it possi ble to test the accuracy of predictions against speaker-specific vocal trac ts and acoustic patterns. Vocal tract dimensions for /r/ derived via magnet ic-resonance imaging (MRI) for two speakers of American English [Alwan, Nar ayanan, and Haker, J. Acoust. Sec. Am. 101, 1078-1089 (1997)] were used to construct models of the acoustics of /r/. Because previous models have not sufficiently accounted for the very low F3 characteristic of /r/, the aim w as to match formant frequencies predicted by the models to the full range o f formant frequency values produced by the speakers in recordings of real w ords containing /r/. In one set of experiments, area functions derived from MRI data were used to argue that the Perturbation Theory of tube acoustics cannot adequately account for /r/, primarily because predicted locations d id not match speakers' actual constriction locations. Different models of t he acoustics of /r/ were tested using the Maeda computer simulation program [Maeda, Speech Commun. 1, 199-299 (1982)]; the supralingual vocal-tract di mensions reported in Alwan et al. were found to be adequate at predicting o nly the highest of attested F3 values. By using (1) a recently developed ad aptation of the Maeda model that incorporates the sublingual space as a sid e branch from the front cavity, and by including (2) the sublingual space a s an increment to the dimensions of the front cavity, the mid-to-low values of the speakers' F3 range were matched. Finally, a simple tube model with dimensions derived from MRT data was developed to account for cavity affili ations. This confirmed F3 as a front cavity resonance, and variations in F1 , F2, and F4 as arising from mid- and back-cavity geometries. Possible trad ing relations for F3 lowering based on different acoustic mechanisms for ex tending the front cavity are also proposed. (C) 2000 Acoustical Society of America. [S0001-4966(00)00407-0].