A source generator based modeling framework for synthesis of speech under stress

The objective of this paper is to formulate an algorithm to generate stressed synthetic speech from neutral speech using a source generator framework previously employed for stressed speech recognition. The following goals are addressed (i) identify the most visible indicators of stress as perceived by the listener in stressed speaking styles such as loud, Lombard effect and angry, (ii) develop a mathematical model for representing speech production under stressed conditions, and (iii) employ the above model to produce emotional/stressed synthetic speech from neutral speech. The stress modeling scheme is applied to an existing low-bit rate CELP speech coder in order to investigate (i) the coder´s ability and limitations reproducing stressed synthetic speech, and (ii) our ability to perturb coded neutral speech parameters at the synthesis stage so that resulting speech is perceived as being under stress. Two stress perturbation algorithms are proposed and evaluated. Results from formal listener evaluations show that 87% of neutral perturbed speech was indeed perceived as stressed