Verifying a vocal tract model with a closed side-branch.

In this article an implementation of a vocal tract model and its validation are described. The model uses a transmission line model to calculate pole and zero frequencies for a vocal tract with a closed side-branch such as a sublingual cavity. In the validation study calculated pole and zero frequencies from the model are compared with frequencies estimated using elementary acoustic formulas for a variety of vocal tract configurations.

Acoustic modeling of American English /r/.

Recent advances in physiological data collection methods have made it possible to test the accuracy of predictions against speaker-specific vocal tracts and acoustic patterns. Vocal tract dimensions for /r/ derived via magnetic-resonance imaging (MRI) for two speakers of American English [Alwan, Narayanan, and Haker, J. Acoust. Soc. 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 was to match formant frequencies predicted by the models to the full range of formant frequency values produced by the speakers in recordings of real words 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 did not match speakers' actual constriction locations. Different models of the acoustics of /r/ were tested using the Maeda computer simulation program [Maeda, Speech Commun. 1, 199-299 (1982)]; the supralingual vocal-tract dimensions reported in Alwan et al. were found to be adequate at predicting only the highest of attested F3 values. By using (1) a recently developed adaptation of the Maeda model that incorporates the sublingual space as a side branch from the front cavity, and by including (2) the sublingual space as 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 MRI data was developed to account for cavity affiliations. This confirmed F3 as a front cavity resonance, and variations in F1, F2, and F4 as arising from mid- and back-cavity geometries. Possible trading relations for F3 lowering based on different acoustic mechanisms for extending the front cavity are also proposed.

Articulatory tradeoffs reduce acoustic variability during American English /r/ production.

The American English phoneme /r/ has long been associated with large amounts of articulatory variability during production. This paper investigates the hypothesis that the articulatory variations used by a speaker to produce /r/ in different contexts exhibit systematic tradeoffs, or articulatory trading relations, that act to maintain a relatively stable acoustic signal despite the large variations in vocal tract shape. Acoustic and articulatory recordings were collected from seven speakers producing /r/ in five phonetic contexts. For every speaker, the different articulator configurations used to produce /r/ in the different phonetic contexts showed systematic tradeoffs, as evidenced by significant correlations between the positions of transducers mounted on the tongue. Analysis of acoustic and articulatory variabilities revealed that these tradeoffs act to reduce acoustic variability, thus allowing relatively large contextual variations in vocal tract shape for /r/ without seriously degrading the primary acoustic cue. Furthermore, some subjects appeared to use completely different articulatory gestures to produce /r/ in different phonetic contexts. When viewed in light of current models of speech movement control, these results appear to favor models that utilize an acoustic or auditory target for each phoneme over models that utilize a vocal tract shape target for each phoneme.

Coarticulatory organization for lip rounding in Turkish and English.

A number of studies, involving English, Swedish, French, and Spanish, have shown that, for sequences of rounded vowels separated by nonlabial consonants, both EMG activity and lip protrusion diminish during the intervocalic consonant interval, producing a "trough" pattern. A two-part study was conducted to (a) compare patterns of protrusion movement (upper and lower lip) and EMG activity (orbicularis oris) for speakers of English and Turkish, a language where phonological rules constrain vowels within a word to agree in rounding and (b) determine which of two current models of coarticulation, the "look-ahead" and "coproduction" models, best explained the data. Results showed Turkish speakers producing "plateau" patterns of movement rather than troughs, and unimodal rather than bimodal patterns of EMG activity. In the second part of the study, one prediction of the coproduction model, that articulatory gestures have stable profiles across contexts, was tested by adding and subtracting movement data signals to synthesize naturally occurring patterns. Results suggest English and Turkish may have different modes of coarticulatory organization.

Oral feeding after total laryngectomy.

Pharyngocutaneous fistulae occur in 15%-25% of patients after total laryngectomy. Factors that may predispose to fistulae formation include prior radiation, surgical technique, tumor size and location, and patient nutritional status. In addition, many surgeons believe that the timing of oral feeding after surgery contributes to fistula development. Thus, they advocate delaying feeding postoperatively, especially in high-risk patients. The traditional guideline has been to wait until the seventh postoperative day. The purpose of this study was to examine the relationship between the timing of postoperative oral feeding and the development of pharyngocytaneous fistulae after total laryngectomy with primary closure in patients with squamous cell carcinoma. A questionnaire was sent to 210 members of the American Society for Head and neck Surgery to determine practice patterns toward feeding after laryngectomy. We also reviewed the records of 137 patients who underwent total laryngectomy at the University of Colorado Health Sciences Center and the Denver VA Medical Center from January 1975 through December 1987. Of the surgeons polled, 84.5% waited at least 7 days after surgery to begin oral feeding. However, in reviewing 94 patients eligible for study, we found no difference in the rate of fistula formation between patients fed on or before the fifth postoperative day and those fed on or after the sixth postoperative day. In fact, most fistulae were evident before the patient started oral feeding. Pyriform sinus tumors were predisposed to fistulae but prior radiotherapy and neck dissection seemed to have no effect. Earlier oral feeding after total laryngectomy may improve patient comfort and shorten hospital stay without increasing the incidence of complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Hearing results and control of vertigo after retrolabyrinthine vestibular nerve section.

To determine the effect of retrolabyrinthine vestibular nerve section (RVNS) on hearing, vertigo, and associated symptoms, we reviewed our experience in 48 patients. Of the 48, 39 responded to a questionnaire. Although RVNS appeared to have little effect on hearing in Meniere's patients, 91% of non-Meniere's patients had significant and often delayed postoperative sensorineural hearing loss. Our results for vertigo control compared favorably to previous reports with 96% of Meniere's patients and 69% of non-Meniere's patients reporting improvement. Presently, we more frequently recommend RVNS as the primary procedure for the control of severe vertigo in Meniere's patients. Patients with vertigo from other causes must be carefully selected.