| 摘要 |
PROBLEM TO BE SOLVED: To securely detect a pitch even when the pitch cycle of a voiced sound of an analytic synthesis system speech encoding system is long, when no pitch waveform appears in an analytic frame, and when there is power envelope variation in the analytic frame. SOLUTION: The cross correlation r(i) between the predictive residue signal of a current frame obtained by an LPC analyzer 1 and an inverse filter 2 and the predictive residue signal of the last frame stored in predictive residue buffers 4 and 5 is found. After normalization with a cross correlation value r(0) of 0th order is performed, weighting is carried out and a maximum value other than i=0 is detected and compared with a decision threshold valueθ; when r(τ)<=θ, a voiceless sound is decided and a pitch cycle T is set to 0, but when r(τ)>=θ, a voiced sound is decided and T=τis outputted.
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