Extraction of aortic and pulmonary components from second heart sound

An extraction method based on simulated annealing (SA) algorithm was proposed to estimate the aortic valve component (A component) and pulmonary valve component (P component) from a second heart sound (S2). It was assumed that both A and P components are subject to envelope modulated chirp model. Each component was characterized by 9 parameters. A S2 signal is thus represented by 18 parameters in total. Under mean squared error (MSE) criterion, the optimal parameters of A component and P component were estimated by using SA algorithm. The A and P components were then reconstructed. Simulation results showed that, the MSEs of reconstructed A and P components are less than 1% and 8% for noise-free condition; the MSEs were less than 1.5% and 10% for - 15 dB additive Gaussian white noise condition. In further applications, A and P components are extracted from S2 signals of 10 subjects. The end timing and start timing of reconstructed A and P components were further verified by the dicrotic notches for 2 subjects.