Phrase classes in two-level language models for ASR

  • Authors:
  • Raquel Justo;M. Inés Torres

  • Affiliations:
  • University of the Basque Country, Department of Electricity and Electronics, 48940, Leioa, Spain;University of the Basque Country, Department of Electricity and Electronics, 48940, Leioa, Spain

  • Venue:
  • Pattern Analysis & Applications
  • Year:
  • 2009

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Abstract

In this work, we propose and compare two different approaches to a two-level language model. Both of them are based on phrase classes but they consider different ways of dealing with phrases into the classes. We provide a complete formulation consistent with the two approaches. The language models proposed were integrated into an Automatic Speech Recognition (ASR) system and evaluated in terms of Word Error Rate. Several series of experiments were carried out over a spontaneous human–machine dialogue corpus in Spanish, where users asked for information about long-distance trains by telephone. It can be extracted from the obtained results that the integration of phrases into classes when using the language models proposed leads to an improvement of the performance of an ASR system. Moreover, the obtained results seem to indicate that the history length with which the best performance is achieved is related to the features of the model itself. Thus, not all the models show the best results with the same value of history length.