Heart Sound Lab Report

INTRODUCTION

Phonocardiogram is a physiological signal that results from the vibrations created by closure of heart valves and it represents the recording of the heart sound signal. A normal cardiac cycle is comprised of two major sounds- first sound (S1) and the second heart sound (S2). The first heart sound has four components in it, due to the closure of AV and semilunar valves. The second heart sound has two components, one due to closure of aortic valve and another due to closure of pulmonary valve (Rangayyan, R.M and Lehner ,R.J (1988). In some case a third heart sound (S3) may be heard, which is corresponding to sudden termination of the ventricular rapid filling phase. In late diastole, a fourth heart sound (S4) may be heard, caused

Its main advantage is to provide simultaneous information on frequency and time location of the signal characteristics in terms of the representation of the signal at multiple resolutions corresponding to different time scales. Derek Abott et al., (2001), demonstrated that wavelet denoising techniques in combination with averaging are useful for removing white noise from heart sounds. They have also concluded that a decomposition level of 5 produced reasonable results and the signal produced marginal benefits while the computation time is increased during decomposition. Averaging is done to reduce the noise and produce a characteristic heart beat. Jalel Chebil et al., (2007) utilized the discrete wavelet transforms to identify the first heart sound S1, second heart sound S2, and murmurs and developed an algorithm to classify the PCG signal into 3 categories as signal with murmur, signal with diastolic murmur, or a normal signal. P.S.Vikhe et al., (2009) used Discrete Wavelet Transform (DWT) and Continuous Wavelet Transform (CWT) to analyze the first (S1) and second (S2) heart sound of the Phonocardiogram signal (PCG). The experiments were performed on normal and pathological PCG signals. DWT was used to denoise and find the split between A2 and P2 and CWT was used to determine the frequency components of S1 and S2 of PCG and to measure the split between A2 and

From the above figure 7, the frequency split was more evident when the decomposed level increased. The s1 starts from 0.3 to 0.38 sec( four distinct energy band ) , s2 starts from 0.6 to 0.7 sec (two distinct energy band) at third level approximation the frequency with respect to time is more evident .

Abnormal condition 1 (Mid systolic click)

Mid Systolic click is a high-frequency sound in mid systole that results from the abrupt halting of prolapsing mitral valve leaflets' excursion into the atrium by chordae. This was reflected in the PCG signal as a click between S1 and S2 shown in below figure