Unit database pruning based on the cost degradation criterion for concatenative speech synthesis

A novel method of unit database pruning for concatenative speech synthesis is proposed. The proposed method uses sums of the unit preference criterion, which are calculated from cost degradation from the optimal sequence, instead of the appearance frequencies of units, which is used in the conventional method. Therefore, the proposed method is an extension of the conventional method. Since not only the optimal units but also the other candidate units can be taken into account for pruning, unit databases can be pruned with less experimental speech synthesis. The results of a unit selection experiment on 4-hour pruned unit databases built from the original 10.6-hour database indicate that the amount of the experimental speech synthesis can be reduced to 25% of that required for the conventional method without loss of the quality of synthetic speech in terms of average cost.