This paper proposes an algorithm to improve the performance of the noise power spectrum estimation using the minimum statistics (MS). The minimum statistics noise estimator (MSNE) that is most efficient for speech enhancement often underestimates noise power when the signal characteristics changes abruptly. The proposed algorithm improves the accuracy of noise estimation by removing harmonic components of the speech signal. Simulation results verify that the performance of the proposed algorithm is better than that of the conventional algorithm in terms of the segmental SNR (SegSNR) and the spectral distance (SD).

This letter presents the advantages of a cascaded algebraic codebook structure at relatively high bit-rates. The cascaded structure that consists of two stages provides flexible pulse combinations due to an additional gain term in the second stage. The perceptual quality of the cascaded structure can be further improved by using a gain re-estimation scheme. Experiments confirm that the cascaded structure has a big advantage in terms of quality and complexity as the bit-rate becomes higher.