Bilingual acoustic modeling with state mapping and three-stage adaptation for transcribing unbalanced code-mixed lectures

This paper presents a bilingual acoustic modeling approach for transcribing Mandarin-English code-mixed lectures with highly unbalanced language distribution. Special terminologies for the content were produced in the guest language of English (about 15%) and embedded in the utterances produced in the host language of Mandarin (about 85%). The code-mixing nature of the target corpus and the very small percentage of the English data made the task difficult. State mapping and merging approaches plus three stages of model adaptation handles the above problem. Significant improvements in recognition accuracy were obtained in the experiment with a real bilingual code-mixed lecture corpus recorded at National Taiwan University. The code-mixing situation considered is actually very natural in the spoken language of the daily lives of many people in the globalized world today.