The Research And Implementation Of Algorithm Of Isolated Word Speech Recognition

The research object in Speech recognition technology is based on speech signal processing. This paper studies the algorithm and implementation of small vocabulary, speaker-independent, Chinese words, isolated word recognition.The article first introduced the Hidden Markov Model (HMM), including HMM parameter estimation, Viterbi algorithm. Then explains how to build speech recognition system using HMM.HMM were discussed based on discrete HMM (DHMM) and continuous HMM (CHMM).The main difference between CHMM and DHMM is that the probability distribution function of observations. DHMM's probability distribution function of observations is discrete probability, while the CHMM is a continuous probability density, In commonly CHMM uses Gaussian mixture model (GMM) as the probability density function. DHMM has the advantages of the small computational load, the less of storage, but the existence of quantization error will lead to the lower recognition accuracy compare to CHMM.In the practical application of speech recognition systems, the speech of out of vocabulary (OOV) input on voice recognition system will cause unpredictable results, which is need to avoid in the design,so studying rejection algorithm become very important. In general, the realization of rejection algorithm has two ways, one is to use garbage model, the second is the use of the existing results of the recognition. The first method requires additional training data, and generally difficult to select the appropriate data of garbage. Therefore, in general application we choose the second method. This paper studied the results of recognition, and ultimately chosen the difference between largest and second largest between the recognition probability as the basis of rejection algorithm.It is difficult to simulate the practical application environment of the speech recognition systems, such as the interference of background noise, voice, real-time input and real-time signal processing. This paper introduced the implementation of isolated speech recognition on TI' s DM642 DSP ,including how to input the speech signal, and realization of VAD algorithm.