A mouth opening effect based on pole modification for expressive singing voice transformation
Résumé
Improving expressiveness in singing voice synthesis systems requires to perform realistic timbre transformations, e.g. for varying voice intensity. In order to sing louder, singers tend to open their mouth more widely, which changes the vocal tract’s shape and resonances. This study shows, by means of signal analysis and simulations, that the main effect of mouth opening is an increase of the 1st formant’s frequency (F1) and a decrease of its bandwidth (BW1). From these observations, we then propose a rule for producing a mouth opening effect, by modifying F1 and BW1, and an approach to apply this effect on real voice sounds. This approach is based on pole modification, by changing the AR coefficients of an estimated all-pole model of the spectral envelope. Finally, listening tests have been conducted to evaluate the effectiveness of the proposed effect.