Volume 128, Issue 2, August 2010
Index of content:
- SPEECH PRODUCTION 
128(2010); http://dx.doi.org/10.1121/1.3458839View Description Hide Description
Unilateral laryngeal paralysis leads to tension imbalance and hence to asynchronous movements between the two vocal folds during phonation. In the current study, a computational model of phonation that couples a two-mass model of the vocal folds with a Navier-Stokes model of the glottal airflow, has been used to examine the dynamics of vocal fold configurations with tension imbalance and its implications for phonation. The simulations show that tension imbalance influences phonation onset, intensity as well as the fundamental phonation frequency. Distinct non-linear effects such as period-doubling bifurcation and preferential frequency selection are also observed.
128(2010); http://dx.doi.org/10.1121/1.3455838View Description Hide Description
This study used a symmetric, three-dimensional, physical model of the larynx called M6 in which the transverse plane of the glottis is formed by sinusoidal arcs for each medial vocal fold surface, creating a maximum glottal width of 0.16 cm at the location of the minimal glottal area. Three glottal angles were studied: convergent 10°, uniform (0°), and divergent 10°. Fourteen pressure taps were incorporated in the upstream-downstream direction on the vocal fold surface at three coronal locations, at the one-fourth, one-half, and three-fourths distances in the anterior-posterior direction of the glottis. The computational software FLUENT was used to compare and augment the data for these cases. Near the glottal entrance, the pressures were similar across the three locations for the uniform case; however, for the convergent case the middle pressure distribution was lower by 4% of the transglottal pressure, and lower by about 2% for the divergent case. Also, there were significant secondary velocities toward the center from both the anterior commissure and vocal process regions (of as much as approximately 10% of the axial velocities). Thus, the three dimensionality created relatively small pressure gradients and significant secondary velocities anteriorly-posteriorly within the glottis.
128(2010); http://dx.doi.org/10.1121/1.3459842View Description Hide Description
This study characterizes the speechtempo (articulation rate, excluding pauses) of two distinct varieties of American English taking into account both between-speaker and within-speaker variation. Each of 192 speakers from Wisconsin (the northern variety) and from North Carolina (the southern variety), men and women, ranging in age from children to old adults, read a set of sentences and produced a spontaneous unconstrained talk. Articulation rate in spontaneous speech was modeled using fixed-mixed effects analyses. The models explored the effects of the between-speaker factors dialect, age and gender and included each phrase and its length as a source of both between- and within-speaker variation. The major findings are: (1) Wisconsin speakers speak significantly faster and produce shorter phrases than North Carolina speakers; (2) speechtempo changes across the lifespan, being fastest for individuals in their 40s; (3) men speak faster than women and this effect is not related to the length of phrases they produce. Articulation rate in reading was slower than in speaking and the effects of gender and age also differed in reading and spontaneous speech. The effects of dialect in reading remained the same, showing again that Wisconsin speakers had faster articulation rates than did North Carolina speakers.