Combining stochastic and linguistic language models for recognition of spontaneous speech

We present a new approach of combining stochastic language models and traditional linguistic models to enhance the performance of our spontaneous speech recognizer. We compile arbitrary large linguistic context dependencies into a category based bigram model which allows us to use a standard beam-search driven forward Viterbi algorithm for real time decoding. Since this recognizer is used in a dialog system, the information about the last system utterance is used to build dialogstep dependent language models. This setup is verified and tested on our corpus of spontaneous speech utterances collected with our dialog system. Experimental results show a significant reduction of word error rate