Concatenation of speech segments by use of a speech synthesizer

A speech synthesizer apparatus comprising:

• first storage means for storing speech segments of speech waveform signals of natural utterance;
• speech analyzing means, based on the speech segments of the speech waveform signals stored in said first storage means and a phoneme sequence corresponding to the speech waveform signals, for extracting and outputting index information on each phoneme of the speech waveform signals, first acoustic feature parameters of each phoneme indicated by the index information, and prosodic feature parameters for each phoneme indicated by the index information;
• second storage means for storing the index information, the first acoustic feature parameters, and the prosodic feature parameters outputted from said speech analyzing means;
• weighting coefficient training means for calculating acoustic distances in second acoustic feature parameters between one target phoneme from the same phonemic kind and the phoneme candidates other than the target phoneme based on the first acoustic feature parameters and the prosodic feature parameters which are stored in said second storage means, and for determining weighting coefficient vectors for respective target phonemes defining degrees of contribution to the second acoustic feature parameters for respective phoneme candidates by executing a predetermined statistical analysis for each of the second acoustic feature parameters for respective phoneme candidates based on the calculated acoustic distances;
• third storage means for storing weighting coefficient vectors for the respective target phonemes determined by the weighting coefficient training means;
• speech unit selecting means, based on the weighting coefficient vectors for the respective target phonemes stored in said third storage means, and the prosodic feature parameters stored in said second storage means, for searching for a combination of phoneme candidates which correspond to a phoneme sequence of an input sentence and which minimizes a cost including a target cost representing approximate costs between a target phoneme and the phoneme candidates and a concatenation cost repenting approximate costs between two phoneme candidates and a concatenation cost representing approximate costs been two phoneme candidates to be adjacently concatenated, and for outputting index information on the searched out combination of phoneme candidates, said target cost being represented by either one of a predetermined non-linear multiplication and a predetermined non-linear combination, with use of predetermined suitability functions each of fuzzy membership function, said concatenation cost being represented by either one of another predetermined non-linear multiplication and another predetermined non-linear combination with use of another predetermined suitability functions each of fuzzy membership function;
• and
• speech synthesizing means for synthesizing and outputting a speech signal corresponding to the input phoneme sequence by sequentially reading out speech segments of speech waveform signals corresponding to the index information from said first storage means based on the index information outputted from said unit selecting means, and by concatenating the read-out speech segments of the speech waveform signals.