Training of error-corrective model for ASR without using audio data

This paper introduces a method to train an error-corrective model for Automatic Speech Recognition (ASR) without using audio data. In existing techniques, it is assumed that sufficient audio data of the tar get application is available and negative samples can be prepared by having ASR recognize this audio data. However, this assumption is not always true. We propose generating probable N-best lists, which the ASR may produce, directly from the text data of the target application by taking phoneme similarity into consideration. We call this process "Pseudo-ASR". We conduct discriminative reranking with the error-corrective model by regarding the text data as positive samples and the N-best lists from the Pseudo-ASR as negative samples. Experiments with Japanese call center data showed that discriminative reranking based on the Pseudo-ASR improved the accuracy of the ASR.