Instantaneous frequency estimate of nonstationary phonocardiograph signals using hilbert spectrum.

A method for analyzing the nonlinear and non-stationary processes and investigating the instantaneous frequency of the practical medical signals is presented. The aim of this contribution is to explore the role that both empirical mode decomposition and Hilbert transform can be applied to play in phonocardiograph (PCG) signals. Hilbert transform is used to each intrinsic mode function to obtain the global time-frequency distribution of the underlying signal with a point of view of instantaneous frequency. Two kinds of clinical phonocardiograph signals with normal and abnormal cardiac functions were analyzed by using the proposed approach. The instantaneous frequency distributions of the PCG signals were also compared with the results by using the Morlet wavelet transform. Both simulation and experimental results were presented and discussed to demonstrate the power and effectiveness of the proposed approach.