The line spectrum pair (LSP) estimation method by using the extended Kalman filter (EKF) has been proposed. The EKF is very useful to estimate the LSP parameters directly from speech signals. The tracking ability of the EKF deteriorates in the regions where the signal decreases gradually, and incorrect formants are often estimated. In order to improve the tracking ability, the proposed method employs the time-varying values that can be controlled for each LSP parameter independently. The time-varying values are adjusted corresponding to the unevenness of the residual degree of signal in the frequency domain. The rasidual signal is divided into several sub-bands through the filter banks. The unevenness is detected by using cluster analysis.
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