Using Bayesian Networks to find relevant context features for HMM-based speech synthesis

Speech units are highly context-dependent, so taking contextual features into account is essential for speech modelling. Context is employed in HMM-based Text-to-Speech speech synthesis systems via context-dependent phone models. A very wide context is taken into account, represented by a large set of contextual factors. However, most of these factors probably have no significant influence on the speech, most of the time. To discover which combinations of features should be taken into account, decision tree-based context clustering is used. But the space of context-dependent models is vast, and the number of contexts seen in the training data is only a tiny fraction of this space, so the task of the decision tree is very hard: to generalise from observations of a tiny fraction of the space to the rest of the space, whilst ignoring uninformative or redundant context features. The structure of the context feature space has not been systematically studied for speech synthesis. In this paper we discover a dependency structure by learning a Bayesian Network over the joint distribution of the features and the speech. We demonstrate that it is possible to discard the majority of context features with minimal impact on quality, measured by a perceptual test. Index Terms: HMM-based speech synthesis, Bayesian Networks, context informatio

Transfer Learning for Speech and Language Processing

Transfer learning is a vital technique that generalizes models trained for one setting or task to other settings or tasks. For example in speech recognition, an acoustic model trained for one language can be used to recognize speech in another language, with little or no re-training data. Transfer learning is closely related to multi-task learning (cross-lingual vs. multilingual), and is traditionally studied in the name of `model adaptation'. Recent advance in deep learning shows that transfer learning becomes much easier and more effective with high-level abstract features learned by deep models, and the `transfer' can be conducted not only between data distributions and data types, but also between model structures (e.g., shallow nets and deep nets) or even model types (e.g., Bayesian models and neural models). This review paper summarizes some recent prominent research towards this direction, particularly for speech and language processing. We also report some results from our group and highlight the potential of this very interesting research field.Comment: 13 pages, APSIPA 201

Review of Research on Speech Technology: Main Contributions From Spanish Research Groups

In the last two decades, there has been an important increase in research on speech technology in Spain, mainly due to a higher level of funding from European, Spanish and local institutions and also due to a growing interest in these technologies for developing new services and applications. This paper provides a review of the main areas of speech technology addressed by research groups in Spain, their main contributions in the recent years and the main focus of interest these days. This description is classified in five main areas: audio processing including speech, speaker characterization, speech and language processing, text to speech conversion and spoken language applications. This paper also introduces the Spanish Network of Speech Technologies (RTTH. Red Temática en Tecnologías del Habla) as the research network that includes almost all the researchers working in this area, presenting some figures, its objectives and its main activities developed in the last years