The Research Of Speech Pitch Determination Based On LV-AMDF

Pitch period is one of the important parameter in the analysis and synthesis of speech signals. Pitch period information is used in various applications such as speech coding, pitch synchronous speech analysis and synthesis and speech recognition. However the task of the estimating pitch is very difficult because of the pitch's properties. Therefore, no one algorithm that has been developed so far performs perfectly for different speakers, different applications and different environmental condition.There are many traditional pitch detections, such as: AUTOC, AMDF, CEP, STFT, Wavelet Transform, SIFT and so on. AUTOC needs the center clipping, and its noise immunity is low because of the difficulty for finding out the threshold. The last three perform better, but they are complicated for they need too much multiplication,and they are not suitable for the real-time imbedded equipments,that have shortage for their limited CPU and memory resources.According to the limitation and the stability of the speech pitch, the paper improves the LV-AMDF method, and initiates an adaptive speech pitch determination method. In the unstable speech, it can acquire the exact speech pitch according to the trough in the current window and the windows before by the simple trough-select system, in the stable speech this method can reduce the times of the speech pitch comparison, decreacing the computing cost. This paper also improves the method, which can acquire more accurate point for searching the beginning and ending point of the sonant. Simulations showed that the pitch extracting results of the improved method reduce the rate of the half and double speech pitch point in the speech in different SNR environment.