The Analysis Of The Instantaneous Frequency And Its Application In The Heart Sound Signals Processing

In the clinical work of the cardiac treatment, the abstraction and monitoring of the heart sound characters, as one of the important methods of the cardiac treatment, are being emphasized by many clinical doctors and cardiac researchers incessantly. Traditionally, doctors analyzed the signals by means of the conventional time space or frequency space approach on the presumption that signals are stationary. However, the heart sound signal is not stationary. To analyze and deal with non-stationary signals, people developed the signal analysis theory and forwarded many time-frequency analysis approaches. Otherwise, the research on the time-frequency analysis technology in the bio-medical field is not mature, especially the abstraction of the information in the heart sound signals. Therefore, it is of great significance to search for a time-frequency analysis approach with the high difference rate and more efficiency. This paper makes a try for the application in this field.This paper begins with the instantaneous frequency analysis, and follows the introduction of a new time-frequency analysis approach, Hilbert spectral analysis method, and its application to heart sounds signals. The differences in the performance of the short Fourier Transform, continuous wavelet transform and Hilbert spectrum in time-frequency analysis of heart sound signals are studied and compared in this paper. Conventional Fourier-based methods are insufficient for analyzing non-stationary data. This paper illustrates that this method is adequate for non-stationary data, such as heart sounds signals. This new method gives a more precise definition of particular events in time-frequency space than the short Fourier Transform and wavelet analysis. We can use the method to resolve changes in the frequency content of the heart sound signals.The experiment proves that the application of this approach in the tune-frequency analysis of the heart sound signals can get a satisfying result. It also shows this application has great significance in the clinical treatment and can be a new method of monitoring the cardiac illness.