Optimizing sub-cost functions for segment selection based on perceptual evaluations in concatenative speech synthesis

In concatenative speech synthesis, various factors affect the naturalness of synthetic speech. A cost for segment selection is calculated by integrating some sub-costs capturing the degradation of naturalness caused by such factors. In this paper, we optimize each sub-cost function for converting a linguistic feature or an acoustic parameter into a sub-cost based on perceptual evaluations. Two types of perceptual experiments are performed with test sets constructed by controlling the variations of sub-costs to evaluate the independent effect of each sub-cost and the interactions between them. We clarify the effectiveness of perceptually optimizing subcost functions from a result of a preference test comparing synthetic speech before and after the optimization.