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UBC Theses and Dissertations

Talking tube : a novel approach for vocal tract acoustic modelling using the finite-difference time-domain method Mohapatra, Debasish Ray

Abstract

The human voice is a complex but unique physiological process. It involves the neuromuscular control of articulators to form an intricate upper vocal tract geometry, which yields different speech sounds. The existing computational vocal tract models have significant limitations concerning acoustic precision and simulation performance. The high-dimensional vocal tract models can compute precise acoustic wave propagation at the expense of simulation run-time. This thesis aims to fill these lacunae through two major contributions. Firstly, we introduce a novel vocal tract that extends the existing two-dimensional (2D) vocal tract modelling approach while having three-dimensional behaviour. The proposed model (2.5D FDTD) employs the Finite-Difference Time-Domain numerical scheme to discretize and compute acoustic components on a staggered grid. The simulated acoustic outputs of our new model are shown to match with the 2D FDTD vocal tract model at a low spatiotemporal resolution for open static vocal tract shapes. Contrary to 2D FDTD, the model adds tube depth as an additional impedance parameter to the acoustic wave solver by lumping off-plane waves. This technique offers an excellent balance between computational cost and acoustic precision while promising better geometrical flexibility for vocal tract modelling. Secondly, we tested the model's basic capabilities through the acoustic simulation of cardinal English vowel sounds. For realistic modelling of vowel sounds, we built a vocal tract radiation model. We also couple the 2.5D vocal tract with a self-oscillatory lumped-element vocal fold model to illustrate a fully connected articulatory speech synthesizer. This study offers a speech synthesis tool that can generate static vowel sounds and set up a new pathway for lightweight vocal tract modelling and other computational acoustic research.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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