The Influence of Low Bit Rate Speech Coders on Speech Recognition System
Hui Cui · Jisuanji yingyong yanjiu · 2003
Speech recognition through narrow band channel is important in many areas.At the bit rate as low as 2.4kbps,we can obtain synthetic speech with high intelligibility by speech coding.However,such speech signal has been damaged severely compared with the uncoded one.The low bit rate speech coding has great effect on the following speech recognition.So we must find a way to mitigate the damage of coding.We select three low bit rate vocoder working at 2.4kbps,using LPC(Linear Predictive Coding),MELP(Mixed Excitation Linear Prediction) and IMBE(Improved Multiband Excitation) algorithms respectively,to find the difference of their influences on speech recognition.Using different feature vectors,the effect of the vocoders differs on speaker dependent continuous speech recognition and speaker independent connected digits recognition.The results of the experiments have shown important relation between the algorithm structures of the vocoder and recognition system.It is helpful to use similar structures to improve the recognition performance.It will also be useful to change the way of extracting feature parameters for the recognition.