Abstract: A method of pitch extraction by Linear Prediction Code (LPC) analysis with predeter-ming voiced sounds is presented in this paper. At first, the voiced parts in speech signal is identified by the difference a₀-a₁, where a₀=1 and a1 is the first coefficient of linear predictor, then only the voiced parts are processed to extract the pitch period. When pitch detecting, the data rate is compressed by half, the 8 coefficients of inverse filter are calculated by autocorrelation LPC method, and then for the residual signal, the output of the inverse filter, the pitch period is extracted by the Average Magnitude Difference Function (AMDF) method, and the curve of pitch period is linearly interpolated and nonlinearly filtered.
The results obtained by our method is compared with those obtained by a semi-automatic pitch detector and by SIFT method. It is shown that the algorithm presented in this paper is quite precise and effective for continuous speech with background noise below 40 dB. It is unnecessary toalculate the pitch periods in voiceless sounds and silence periods, and the classification of voiced or unvoiced sounds is rather precise.