Effects of a curved vocal tract with grid-generated tongue profile on low-order formants

Abstract

A hyperbolic grid-generation algorithm allows investigation of the effect of vocal-tract curvature on low-order formants. A smooth two-dimensional (2D) curve represents the combined lower lip, tongue, and anterior pharyngeal wall profile as displacements from the combined upper lip, palate, and posterior pharyngeal wall outline. The algorithm is able to generate tongue displacements beyond the local radius of strongly curved sections of the palate. The 2D grid, along with transverse profiles of the lip, oral-pharyngeal, and epilarynx regions, specifies a vocal conduit from which an effective area function may be determined using corrections to acoustic parameters resulting from duct curvature; the effective area function in turn determines formant frequencies through an acoustic transmission-line calculation. Results of the corrected transmission line are compared with a three-dimensional finite element model. The observed effects of the curved vocal tract on formants F1 and F2 are in order of importance, as follows: (1) reduction in midline distances owing to curvature of the palate and the bend joining the palate to the pharynx, (2) the curvature correction to areas and section lengths, and (3) adjustments to the palate-tongue distance required to produce smooth tongue shapes at large displacements from the palate.

Analyses of vocal tract cross-distance to area mapping: An investigation of a set of vowel images

“…Measurements of cross-distances and cross-sectional areas are best done in planes that are orthogonal to the vocal tract axis, which changes as articulation changes. At least approximate corrections when the planes are not orthogonal to the axis should be applied, and even curvature of the vocal tract itself taken into account (i.e., Milenkovic et al, 2010). As more data are obtained a much better understanding of the individual variation in the relation between cross-distance and cross-section area of the vocal tract will be possible.…”

Inter-Speaker Variability: Speaker Normalisation and Quantitative Estimation of Articulatory Invariants in Speech Production for French

“…In turn, the AF can be determined from the Sagittal Function (SF), (i.e. the transverse sagittal distance between the upper and lower VT contours along the midline) using various versions of Heinz & Stevens' [32] model ( [33][34][35][36]). This section presents the calculation of the SF from VT contours as well as an evaluation of its interspeaker variability.…”

Benchmarks for time-domain simulation of sound propagation in soft-walled airways: Steady configurations

“…A question could be raised at the outset of this study about the merit of expending resources on one-dimensional approaches to vocal tract acoustics when three-dimensional approaches with complex geometry are now routine in computational fluid mechanics and aeroacoustics (Vampola et al, 2008;Milenkovic et al, 2010). The simple answer is that real-time (or near real-time) simulations on ordinary home, office, or hand-held computers is still a high priority.…”