Detection of unseen words in conversational Mandarin

We present a Mandarin keyword search system that uses a large vocabulary recognizer to generate consensus networks at various resolutions: word, character, syllable and phone. In order to achieve fast and accurate search, we propose the use of an efficient approximate-match dynamic programming algorithm that finds the best alignment between the target query and the consensus network. Experiments with Mandarin conversational telephone speech show that the approximate-match search improves detection accuracy by more than 10% for rare words that are not present in the recognizer´s dictionary (OOV terms). We also found OOV terms to benefit most from system combination, where we observe a roughly 10% improvement relative to the best single system.