Time-frequency analysis of heart sound based on HHT [Hilbert-Huang transform]

Heart sounds belongs to non-stationary signals. The traditional signal processing methods are constrained. In this paper, a novel time-frequency analysis method based on the Hilbert-Huang transform (HHT) was studied. The principles of HHT were introduced. The heart sound of coronary artery disease (CAD) was analyzed based on HHT. First, decomposing the heart sound into a small number of intrinsic mode functions (IMFs); second, performing the Hilbert transform an each IMF component; then achieving the Hilbert spectrum and marginal spectrum. The results demonstrate that the Hilbert spectrum and marginal spectrum clearly reveal the time-frequency varying characteristics of heart sounds for CAD and indicate the clinical pathology significance of CAD. These establish the basis for early diagnosis of CAD.