Modeling the Vocal Tract Transfer Function Using a 3D Digital Waveguide Mesh

Abstract

The digital waveguide mesh has been shown to be capable of reproducing the acoustic impulse response of cylindrical vocal tract analogs. This study extends the same methodology to three-dimensional simulation of the acoustic response of graphical models of the vocal tract obtained from magnetic resonance imaging for a group of trained subjects. By such simulation of the vocal tract transfer function and convolution with an appropriate source waveform, basic phonemes are resynthesized and compared with benchmark audio recordings. The technologies and techniques used for simulation are described, alongside the protocol for image capture and the process for collection of benchmark audio. The results of simulation and acoustic recording are then evaluated and compared. The value of three-dimensional simulation in comparison to existing lower-dimensionality equivalents is assessed. It is found that while three-dimensional simulation provides a strong representation of the low frequency vocal tract transfer function, at higher frequencies its performance becomes geometry-dependent. MRI imaging and benchmark audio is provided for future studies and to permit comparison with comparable means of acoustic simulation.