The Research Of Small Vocabulary Speaker-Independent Continuous Speech Recognition System

Speech recognition means that computer can understand human's speech and execute certain command or assignment according to phonetic content. It is widely used in many fields such as dial system of telephone, household appliance system of remote control, industry control, information search system and so on. It can be classified into three branches, including isolated word recognition, joint word recognition and continuous speech recognition. This paper is mainly about the research on the development and accomplishment of speaker-independent continuous speech recognition system with a small vocabulary.This paper elaborates the basic principle of continuous speech recognition system in detail, and investigates key techniques such as characteristic withdraw, model choice and verdict rule, which are adopted in identifying process. At the same time, continuous speech recognition system is developed and designed according to virtual instrument technique and on the framework of conception"the software instead of hardware"and theories of digital signal process, while LabVIEW language and MATLAB language are combined together as the method. The application of virtual instrument technique to the speech recognition system enables instrument to be softwared, embodying the thought that "the software is an instrument".With the start of real-time collection of speech signal, through the sound signal pretreatment including preweight, wavelet noise elimination and endpoint examination, silent segment and noisy segment in speech signals are eliminated. Therefore, valid speech segment for speaker feature extraction is provided. Parameter feature retrieve method of the Mel frequency cepstrum coefficient (MFCC) with its step difference coefficient is also used. Then after the system is recognized through Vector Quantization(VQ)-Hidden Markov Model(HMM), and the speaker-independent continuous speech recognition system on the platform of LabVIEW is designed .The results of experiment indicate that the continuous speech recognition system on the platform of LabVIEW has many advantages. For example, speech training is not needed in the same circumstance; it is easy to replant; speech is easy to be collected; and the cost of the system is lower. The correct rate of speech recognition is about 90%, almost up to the application requirement. So the continuous speech recognition system is proved to have practical potential.