The dectalk system for German: A study of the modification of a text-to-speech converter for a foreign language

This paper describes the development of the German version of the DECtalk system, which was originally designed for the American language by D.H. Klatt. The aim of this paper is not only to provide an overview on the problems and difficulties for German text-to-speech conversion, using the cascade/parallel formant synthesizer and on the use of new algorithms for parameter extraction, but also to provide a study of the modification procedure which is necessary to build a new language version for a text-to-speech system which was designed for a different, language. These experiences are important for the future design of multilingual text-to-speech systems because the modification from one language to another language gives automatically the answer to many questions which are interesting for the design of a multilingual system or at least a system which can be easily modified for another language. The paper describes the most important steps that have to be performed during the modification procedure, i.e. text normalization and letter-to-sound rules, description of the used synthesizer, description of the tools used for speech analysis and comparison of synthetic and natural speech, tuning of the stationary parts of the phonemes, transitions, prosodies and generation of different voices.