Incorporating lip protrusion and larynx lowering into a time domain model for articulatory speech synthesis

Acoustic transmission in the vocal tract may be simulated in the time domain using the model of Kelly and Lochbaum. A disadvantage of this simulation is that a fixed number of fixed length sections must be used, so that it cannot be used to model variability in vocal tract length, caused by lip protrusion or larynx lowering. This paper describes a simple modification in which digital filters, derived from transmission line T-sections and including glottal and lip impedance models, are appended at each end of a Kelly-Lochbaum filter. The lengths of the sections may be made continuously variable, allowing the lip and larynx segments of the model to be varied, while maintaining a fixed sampling rate. This new technique is compared with the earlier method due to Strube and is found capable of longer extensions and reduced spectral amplitude distortion. (C) 2000 Academic Press.