Flow separation in the vocal system at the outlet of a constriction causes turbulence and a fluid dynamic pressure loss. In articulatory synthesizers, the pressure drop associated with such a loss is usually assumed to be concentrated at one specific position near the constriction and is represented by a lumped nonlinear resistance to the flow. This paper highlights discontinuity problems of this simplified loss treatment when the constriction location changes during dynamic articulation. The discontinuities can manifest as undesirable acoustic artifacts in the synthetic speech signal that need to be avoided for high-quality articulatory synthesis. We present a solution to this problem based on a more realistic distributed consideration of fluid dynamic pressure changes. The proposed method was implemented in an articulatory synthesizer where it proved to prevent any acoustic artifacts

We present a novel 3D vocal tract model and a method to control the articulatory movements of the model. The vocal tract model consists of 7 wireframe meshes that represent the three dimensional surfaces of the articulators and the vocal tract walls. 23 parameters determine the shape of the meshes. The articulatory movements in terms of the parameter curves are generated from a gestural description of an utterance. The work presented here is an integral part of a complete articulatory speech synthesizer for high quality synthesis

A time domain simulation of acoustic propagation in the vocal tract requires the spatial and temporal discretization of the equations of motion and continuity. In the classic transmission line model of the vocal tract with lumped elements, the spatial discretization is provided by the piece-wise constant area function. The temporal finitedifference approximation of the differential equations can, however, vary from one implementation to the other (e.g., [4] vs. [5]). In this study, we have adopted a general finite-difference scheme that depends on a parameter θ where 0 ≤ θ ≤ 1. As special cases, this general method includes the trapezoid rule (θ = 0.5) as well as the implicit (θ = 1) and explicit (θ = 0) finite-difference schemes. We have examined how formant frequencies and bandwidths of simulated vowels are effected by the choice of θ. The experiments were conducted for the sampling rates of 44.1 kHz and 88.2 kHz and compared with the accurate and thus desirable frequencies and bandwidths measured in frequency domain simulations of the vocal tract. It can be shown that optimal values for θ are slightly above 0.5 depending on the sampling rate.