n-gram and decision tree based language identification for written words

As the demand for multilingual speech recognizers increases, the development of systems which combine automatic language identification, language-specific pronunciation modeling and language-independent acoustic models becomes increasingly important. When the recognition grammar is dynamic and obtained directly from written text, the language associated with each grammar item has to be identified using that text. Many methods proposed in the literature require fairly large amounts of text, which may not always be available. This paper describes a text-based language identification system developed for the identification of the language of short words, e.g., proper names. Two different approaches are compared. The n-gram method commonly used in the literature is first reviewed and further enhanced. We also propose a simple method for language identification that is based on decision trees. The methods are first evaluated in a text-based language identification task. Both methods are also tested as preprocessors for a multilingual speech recognition task, where the language of each text item has to be determined, in order to choose the correct text-to-pronunciation mapping. The experimental results show that the proposed methods perform very well, and merit further development.