Influence of tense, modal and lax phonation on the three-dimensional finite element synthesis of vowel [A]

One-dimensional articulatory speech models have long been used to generate synthetic voice. These models assume plane wave propagation within the vocal tract, which holds for frequencies up to 5 kHz. However, higher order modes also propagate beyond this limit, which may be relevant to produce a more natural voice. Such modes could be especially important for phonation types with significant high frequency energy (HFE) content. In this work, we study the influence of tense, modal and lax phonation on the synthesis of vowel [A] through 3D finite element modelling (FEM). The three phonation types are reproduced with an LF (Liljencrants-Fant) model controlled by the R_dglottal shape parameter. The onset of the higher order modes essentially depends on the vocal tract geometry. Two of them are considered, a realistic vocal tract obtained from MRI and a simplified straight duct with varying circular cross-sections. Long-term average spectra are computed from the FEM synthesised [A] vowels, extracting the overall sound pressure level and the HFE level in the 8 kHz octave band. Results indicate that higher order modes may be perceptually relevant for the tense and modal voice qualities, but not for the lax phonation.