Index of content:
Volume 111, Issue 4, April 2002
- SPEECH PRODUCTION 
111(2002); http://dx.doi.org/10.1121/1.1323716View Description Hide Description
A new numerical model of the vocal folds is presented based on the well-known two-mass models of the vocal folds. The two-mass model is coupled to a model of glottal airflow based on the incompressible Navier–Stokes equations.Glottal waves are produced using different initial glottal gaps and different subglottal pressures. Fundamental frequency, glottal peak flow, and closed phase of the glottal waves have been compared with values known from the literature. The phonation threshold pressure was determined for different initial glottal gaps. The phonation threshold pressure obtained using the flow model with Navier–Stokes equations corresponds better to values determined in normal phonation than the phonation threshold pressure obtained using the flow model based on the Bernoulliequation. Using the Navier–Stokes equations, an increase of the subglottal pressure causes the fundamental frequency and the glottal peak flow to increase, whereas the fundamental frequency in the Bernoulli-basedmodel does not change with increasing pressure.
American and Swedish children’s acquisition of vowel duration: Effects of vowel identity and final stop voicing111(2002); http://dx.doi.org/10.1121/1.1463448View Description Hide Description
Vowel durations typically vary according to both intrinsic (segment-specific) and extrinsic (contextual) specifications. It can be argued that such variations are due to both predisposition and cognitive learning. The present report utilizes acoustic phoneticmeasurements from Swedish and American children aged 24 and 30 months to investigate the hypothesis that default behaviors may precede language-specific learning effects. The predicted pattern is the presence of final consonant voicing effects in both languages as a default, and subsequent learning of intrinsic effects most notably in the Swedish children. The data, from 443 monosyllabic tokens containing high-front vowels and final stop consonants, are analyzed in statistical frameworks at group and individual levels. The results confirm that Swedish children show an early tendency to vary vowel durations according to final consonant voicing, followed only six months later by a stage at which the intrinsic influence of vowel identity grows relatively more robust. Measures of vowelformant structure from selected 30-month-old children also revealed a tendency for children of this age to focus on particular acoustic contrasts. In conclusion, the results indicate that early acquisition of vowel specifications involves an interaction between language-specific features and articulatory predispositions associated with phonetic context.
Gender differences in vocal fold contact computed from electroglottographic signals: The influence of measurement criteria111(2002); http://dx.doi.org/10.1121/1.1456517View Description Hide Description
EGGW is a phonatory parameter that can be derived from electroglottographic (EGG) signals and used to infer the relative degree of vocal fold contact. Vocal fold models predict that men will exhibit medial bulging of their vocal folds during phonation but women will not. These models lead us to expect gender differences in the magnitude of EGGW. Nevertheless, significant gender differences in EGGW for adults with normal voices have not been documented in previous studies when EGGW was computed from criterion lines placed at 25%–40% of the amplitude of the uninverted EGG wave form. We hypothesized that EGGW would better reflect gender differences in vocal fold adductory patterns if EGGW was computed from portions of the wave form that were associated with more vocal fold contact. EGGW was measured for seven men and seven women with normal voices. When EGGW was computed from segments of the wave form that were associated with relatively greater vocal fold contact (i.e., using criterion levels of ⩾55%), findings were consistent with the gender-specific adductory patterns that have been proposed from vocal fold models. Guidelines for appropriate placement of criterion lines when computing EGGW are discussed.