Discriminative lexicon adaptation for improved character accuracy

Abstract

While OOV is always a problem for most languages in ASR, in the Chinese case the problem can be avoided by utilizing character n-grams and moderate performances can be obtained. However, character ngram has its own limitation and proper addition of new words can increase the ASR performance. Here we propose a discriminative lexicon adaptation approach for improved character accuracy, which not only adds new words but also deletes some words from the current lexicon. Different from other lexicon adaptation approaches, we consider the acoustic features and make our lexicon adaptation criterion consistent with that in the decoding process. The proposed approach not only improves the ASR character accuracy but also significantly enhances the performance of a characterbased spoken document retrieval system.