Glottal inverse filtering and vocal tract tuning for the numerical simulation of vowel /a/ with different levels of vocal effort

Voice production models provide valuable information about the human voice generation. However, providing them with expressiveness remains a challenge. This work proposes a methodology to modify vocal effort (VE) in the numerical simulation of vowels using a glottal source Liljencrants-Fant (LF) model and a one-dimensional acoustic model based on the finite element method. Vowels recorded with high, mid, and low VE are inverse-filtered to obtain a glottal source signal, used to estimate the LF model Rd parameter. A tuning algorithm adjusts the vocal tract geometry to match the formants of the analysed vowel. Preliminary results for the vowel /a/ are presented. Objective analyses indicate the relevance of both glottal source and vocal tract changes in reproducing VE. They are also perceptually relevant for low VE, while the glottal source predominates in high VE. Perceptual assessment validates the methodology can convey different levels of VE, particularly low and medium.