A comparative study on methods of Weighted language model training for reranking lvcsr N-best hypotheses

This paper focuses on discriminative n-gram language models for a large vocabulary speech recognition task. Specifically we compare three training methods, Reranking Boosting (ReBst), Minimum Error Rate Training (MERT) and the Weighted Global Log-Linear Model (W-GCLM). They have a mechanism for handling sample weights, which are useful for providing an accurate model and work as impact factors of hypotheses for training. W-GCLM is proposed in this paper. We discuss the relationship between the three methods by comparing their loss functions. We also compare them experimentally by reranking N-best hypotheses under several conditions. We show that MERT and W-GCLM are different types of expansion of ReBst and have different respective advantages. Our experimental results reveal that W-GCLM outperforms ReBst and whether MERT or W-GCLM is superior depends on the training and test conditions.