A Fast Robust 1D Flow Model for a Self-Oscillating Coupled 2D FEM Vocal Fold Simulation

A balance between the simplicity and speed of lumped-element vocal fold models and the completeness and complexity of continuum-models is required to achieve fast high-quality articulatory speech synthesis. We develop and implement a novel self-oscillating vocal-fold model, composed of a 1D unsteady fluid model loosely coupled with a 2D FEM structural model. The flow model is capable of robustly handling irregular geometries, different boundary conditions, closure of the glottis and unsteady flow states. A method for a fast decoupled solution of the flow equations that does not require the computation of the Jacobian is provided. The model is coupled with a 2D real-time finite-difference wave-solver for simulating vocal tract acoustics and a 1D wave-reflection analog representation of the trachea. The simulation results are shown to agree with existing data in literature, and give realistic pressure-velocity distributions, glottal width and glottal flow values. In addition, the model is more than an order of magnitude faster to run than comparable 2D Navier-Stokes fluid solvers, while better capturing transitional flow than simple Bernoulli-based flow models. The vocal fold model provides an alternative to simple lumped-element models for faster higher-quality articulatory speech synthesis.