Overview of NITECH HMM - based speech synthesis system for Blizzard Challenge 2013

This paper describes a hidden Markov model (HMM) based speech synthesis system developed for the Blizzard Challenge 2013. In the Blizzard Challenge 2013, audiobooks are provided as training data. In this paper, we focus on a construction of databases for training acoustic models from audiobooks. An automatic alignment technique based on speech recognition is used for obtaining pairs of audio and transcriptions. We also focus on training high natural and neutral acoustic models from audiobooks. Audiobooks consist of speech with various qualities, styles, emotions, etc. It is necessary to appropriately handle such data for training high quality acoustic models. We pruned unneutral and mistakable speech data from the aligned data with multiple techniques and trained acoustic models normalized differences of speaking styles, recording conditions, and file formats among chapters with adaptive training for each chapter. Subjective evaluation results show that the developed system synthesized the high natural and intelligible speech.