Regularized estimation of cepstrum envelope from discrete frequency points

This paper presents an improved method for the estimation of a continuous frequency-envelope when the value of this envelope is specified only at discrete frequencies. It is based on the Galas/Rodet approach which consists of fitting a cepstral amplitude envelope to the specified frequency points by minimizing a frequency-domain least-squares criterion. This paper introduces a regularization technique which increases the robustness of the estimation procedure. Used in combination with a warped frequency-scale, the proposed method is shown to provide an efficient model for the frequency envelope of speech signals.