Speech synthesis by rule using an optimal selection of non-uniform synthesis units

A synthesis scheme is proposed for the optimal selection and extraction of synthesis units. This synthesis scheme has two advantages in the usage of speech segment units. One is the flexible use of nonuniform synthesis units and the other is the optimal choice of a unit sequence for an input phoneme string using appropriateness measures. In this synthesis system, all phoneme subsequences in each synthesis unit are also used as synthesis units. To facilitate the search for appropriate unit candidates, the phoneme sequence entry dictionary is made for a given speech set. Using this entry dictionary, all candidate unit templates are listed for a given input phoneme string. The most appropriate one is selected based on an appropriateness measure. In addition, the author presents a statistic analysis results of Japanese phoneme sequences based on distributions in the word dictionary and text corpora. This investigation provides an estimate of an appropriate number of Japanese phoneme sequences in this synthesis scheme