This paper proposes a new text-to-speech (TTS) system that utilizes large numbers of speech segments to produce very natural and intelligible synthetic speech. There are two innovations; new multiform synthesis units and a new speech modification algorithm based on a vocoder that offers harmonics reconstruction. The multiform units make it possible to reduce acoustic discontinuities at concatenation points and unnatural sound by preparing synthesis units with various lengths and various F/sub 0/ contours. The new speech modification algorithm, on the other hand, improves the quality of prosody modified speech. This algorithm is extremely effective in synthesizing speech whose prosodic parameters are quite different from those of synthesis units. Listening tests confirm that the new synthesis units yield speech with high intelligibility and naturalness, and that the new speech modification algorithm is superior to all other conventional vocoders and waveform domain algorithms including TD-PSOLA, especially when modifying the F/sub 0/ frequency upward.

Automatic synthesis of speech from arbitrary text requires two basic operations: linguistic analysis of input text and speech waveform generation. The achieved quality of the second stage very much depends on the reliability and richness of information generated in the first stage. In this paper we discuss possibilities and problems of text analysis for multilingual speech synthesis. The language independent approach requires the separation of all the language specific information into the language specific inventory, which is composed of different lexica, various dictionaries and lists. The remaining core represents the language independent text-processing engine.