title: Nonlinear transient chirp signal modeling of the aortic and pulmonary components of the second heart sound.
abstract: This paper describes a new approach based on the time-frequency representation of transient nonlinear chirp signals for modeling the aortic (A2) and the pulmonary (P2) components of the second heart sound (S2). It is demonstrated that each component is a narrow-band signal with decreasing instantaneous frequency defined by its instantaneous amplitude and its instantaneous phase. Each component is also a polynomial phase signal, the instantaneous phase of which can be accurately represented by a polynomial having an order of thirty. A dechirping approach is used to obtain the instantaneous amplitude of each component while reducing the effect of the background noise. The analysis-synthesis procedure is applied to 32 isolated A2 and 32 isolated P2 components recorded in four pigs with pulmonary hypertension. The mean +/- standard deviation of the normalized root-mean-squared error (NRMSE) and the correlation coefficient (rho) between the original and the synthesized signal components were: NRMSE = 2.1 +/- 0.3% and rho = 0.97 +/- 0.02 for A2 and NRMSE = 2.52 +/- 0.5% and rho = 0.96 +/- 0.02 for P2. These results confirm that each component can be modeled as mono-component nonlinear chirp signals of short duration with energy distributions concentrated along its decreasing instantaneous frequency.
authors.affiliation: Laboratoire de génie biomédical, Institut de recherches cliniques de Montréal, Québec, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: L G
authors.initials: LG
authors.lastname: Durand
authors.forename: P
authors.initials: P
authors.lastname: Pibarot
mesh_terms: D000818:Animals; D001021:Aortic Valve / Q000502:physiology; D005583:Fourier Analysis; D006347:Heart Sounds; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology; D016018:Least-Squares Analysis; D011664:Pulmonary Valve / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013552:Swine