Kayoko Yanagisawa

Building HMM-TTS Voices on Diverse Data

The statistical models of hidden Markov model based text-to-speech (HMM-TTS) systems are typically built using homogeneous data. It is possible to acquire data from many different sources but combining them leads to a non-homogeneous or diverse dataset. This paper describes the application of average voice models (AVMs) and a novel application of cluster adaptive training (CAT) with multiple context dependent decision trees to create HMM-TTS voices using diverse data: speech data recorded in studios mixed with speech data obtained from the internet. Training AVM and CAT models on diverse data yields better quality speech than training on high quality studio data alone. Tests show that CAT is able to create a voice for a target speaker with as little as 7 seconds; an AVM would need more data to reach the same level of similarity to target speaker. Tests also show that CAT produces higher quality voices than AVMs irrespective of the amount of adaptation data. Lastly, it is shown that it is beneficial to model the data using multiple context clustering decision trees.

CLUSTER ADAPTIVE TRAINING OF AVERAGE VOICE MODELS

Hidden Markov model based text-to-speech systems may be adapted so that the synthesised speech sounds like a particular person. The average voice model (AVM) approach uses linear transforms to achieve this while multiple decision tree cluster adaptive training (CAT) represents different speakers as points in a low dimensional space. This paper describes a novel combination of CAT and AVM for modelling speakers. CAT yields higher quality synthetic speech than AVMs but AVMs model the target speaker better. The resulting combination may be interpreted as a more powerful version of the AVM. Results show that the combination achieves better target speaker similarity when compared with both AVM and CAT while the speech quality is in-between AVM and CAT.

Multi-stream spectral representation for statistical parametric speech synthesis

In statistical parametric speech synthesis such as Hidden Markov Model (HMM) based synthesis, one of the problems is in the over-smoothing of parameters, which leads to a muffled sensation in the synthesised output. In this paper, we propose an approach in which the high frequency spectrum is modelled separately from the low frequency spectrum. The high frequency band, which does not carry much linguistic information, is clustered using a very large decision tree so as to generate parameters as close as possible to natural speech samples. The boundary frequency can be adjusted at synthesis time for each state. Subjective listening tests show that the proposed approach is significantly preferred over the conventional approach using a single spectrum stream. Samples synthesised using the proposed approach sound less muffled and more natural.