Segment selection considering local degradation of naturalness in concatenative speech synthesis

In this paper, we investigate the effect of using a novel cost, RMS (root mean square) cost, for segment selection for concatenative text-to-speech synthesis. The RMS cost is affected not only by the total degradation of naturalness but also by the local degradation of naturalness. From the results of experiments comparing this approach with segment selection based on a conventional average cost, it is found that: (1) in the segment selection based on the RMS cost a larger number of concatenations causing slight local degradation are performed in order to avoid concatenations causing greater local degradation; and (2) the effect of the RMS cost has little dependence on the size of the corpus. Moreover, we clarify that the naturalness of synthetic speech can be slightly improved by utilizing the RMS cost.