Robust pitch estimation in distant speech signals collected from vehicle

Abstract

Due to significant signal attenuation, the speech signals collected at different distances show degradation in the estimation of speech parameters. Therefore the work presented in this paper proposes an alternate method for improving the F 0 parameter estimation from distant speech (DS) signals which are collected through microphones at various distances. The proposed method achieves improved F 0 estimation by adding a post processing module for the conventional zero frequency filtering (ZFF) method used for F 0 estimation. The conventional ZFF method estimates the F 0 parameters by estimating the impulse like discontinuities at the glottal closure instants (GCIs). Since strength of the impulses are heavily attenuated in the case DS signals by reducing the impulse strengths at the GCIs, the F 0 estimation from the these signals becomes unreliable and inaccurate. Hence the present work proposes an alternate method for enhancing the impulse strength for DS signals by subjecting the one more level of zero frequency filtering to the conventional zero frequency filtered signal at every fixed windows having 25 ms length. The smoothed zero frequency filtered signal windows are further refined by low pass filtering using locally estimated F 0 as cut off frequency. The effectiveness of the proposed method of F 0 estimation using refined ZFF method is confirmed based on the comparative performance analysis with the other existing zero frequency post filtering approaches on the state of the art SPEECON database. The performance of the proposed method are evaluated based on the Gross error rates obtained by comparing the estimated F 0 values computed from the DS signals and with that of the ground truth close speaking speech signals.