Improved tone concatenation rules in a formant-based Chinese text-to-speech system

A set of improved tone concatenation rules to be used in a formant-based Mandarin Chinese text-to-speech system is presented. This system concatenates prestored syllables superimposed by additional tone patterns to obtain speech sentences for unlimited text, with the acoustic properties of each syllable modified by a set of synthesis rules. The tone concatenation rules are the most important among these synthesis rules, because they tell how the tone patterns for the syllables should be modified in an arbitrary sentence under various conditions of concatenating syllables of different tones on both sides. The improved tone concatenation rules are obtained empirically by carefully analyzing the tone pattern behavior under various tone concatenation conditions for many sentences in a database. A total of 14 representative tone patterns are defined for the five tones, and different rules about which pattern should be used under what kind of tone concatenation conditions are organized in detail. Preliminary subjective tests indicate that these rules actually give better synthesized speech for a formant-based Chinese text-to-speech system