Cross-Lingual Language Modeling for Low-Resource Speech Recognition

Abstract

This paper proposes using cross-lingual language modeling with syntactic information for low-resource speech recognition. We propose phrase-level transduction and syntactic reordering for transcribing a resource-poor language and translating it into a resource-rich language, if necessary. The phrase-level transduction is capable of performing <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> cross-lingual transduction. The syntactic reordering serves to model the syntactic discrepancies between the source and target languages. Our purpose is to leverage the statistics in a resource-rich language model to improve the language model of a resource-poor language and at the same time to improve low-resource speech recognition performance. We implement our cross-lingual language model using weighted finite-state transducers (WFSTs), and integrate it into a WFST-based speech recognition search space to output the transcriptions of both resource-poor and resource-rich languages. This creates an integrated speech transcription and translation framework. Evaluations on Cantonese speech transcription and Cantonese to standard Chinese translation tasks show that our proposed approach improves the system performance significantly, with up to 12.5% relative character error rate (CER) reduction over baseline language model interpolation, 6.6% relative CER reduction and 18.5% relative BLEU score improvement, compared to the best word-level transduction approach.