A KOREAN LARGE VOCABULARY SPEECH RECOGNITION SYSTEM FOR AUTOMATIC TELEPHONE NUMBER QUERY SERVICE

In this paper, we introduce a Korean large vocabulary speech recognition system. This system recognizes sentence utterances with a vocabulary size of 1160 words, and is designed for an automatic telephone number query service. The system consists of four subsystems. The first is an acoustic processor recognizing words in an input sentence by a Hidden Markov Model (HMM) based speech recognition algorithm. The second subsystem is a linguistic processor which estimates input sentences from the results of the acoustic processor and determines the following words using syntactic information. The third is a time reduction processor reducing recognition time by limiting the number of candidate words to be computed by the acoustic processor. The time reduction processor uses linguistic information and acoustic information contained in the input sentence. The last subsystem is a speaker adaptation processor which quickly adapts parameters of the speech recognition system to new speakers. This subsystem uses VQ adaptation and HMM parameter adaptation based on spectral mapping. We also present our recent work on improving the performance of the large vocabulary speech recognition system. These works focused on the enhancement of the acoustic processor and the time reduction processor for speaker-independent speech recognition. A new approach for speaker adaptation is also described.