Speech synthesis using a nonlinear energy damping model for the vocal folds vibration effect

From a theoretical viewpoint, the vocal fold vibration affects the vocal tract transfer characteristics through nonlinear time-varying interaction between the glottis and vocal tract. Therefore, it is crucial to investigate and model such effects in order to improve voice quality in parametric rule-based speech synthesis systems. The authors first conducted analytic experiments on the vocal fold vibration effects in formant energy damping patterns and then modeled them by a nonlinear 2nd order differential equation for speech synthesis. They confirmed the feasibility of the nonlinear model by speech wave reconstruction experiments.