On the robustness of the Quasi-Harmonic model of speech

In this paper we discuss the robustness of the Quasi-Harmonic model, QHM, previously suggested for speech analysis and AM-FM decomposition of speech. Assuming a frame by frame analysis, QHM suggests an iterative estimator for the actual frequencies of the speech components at the center of analysis window. In this paper, we show that this is a biased estimator and then, we compute analytically and numerically the bias of the estimator showing its dependence on the type and length of the analysis window. Moreover, we analyze the robustness of the QHM estimator in white Gaussian noise, showing that the suggested iterative estimator asymptotically attains the corresponding Cramer-Rao lower bound even in adverse noisy conditions. Examples of synthetic signals are provided to support our analysis.