Selecting optimal non-uniform units for hierarchical unit selection

For concatenative speech synthesis based on non-uniform unit selection, the key to improve the synthetic quality is the careful designing of measuring criteria respect to the units adopted. With our previous hierarchical non-uniform unit selection framework (Xu et al., 2007), two measurements for selecting optimal non-uniform units during searching at different layers are proposed in this paper, including inter-syllable pitch control and spectra distance by phonetic context. These measures are used as components of our cost function, especially for boundaries in front of syllables starting with voiceless consonants. Experiment shows it outperforms our previous system.