Time-frequency analysis of the first heart sound. Part 1: Simulation and analysis

Abstract

The authors propose a simulated first heart sound (S1) signal that can be used as a reference signal to evaluate the accuracy of time-frequency representation techniques for studying multicomponent signals. The composition of this simulated S1 is based on the hypothesis that an S1 recorded on the thorax over the apical area of the heart is composed of constant frequency vibrations from the mitral valve and a frequency modulated vibration from the myocardium. Essentially, the simulated S1 consists of a valvular component and a myocardial component. The valvular component is modelled as two exponentially decaying sinusoids of 50 Hz and 150 Hz and the myocardial component is modelled by a frequency modulated wave between 20 Hz and 100 Hz. The study shows that the simulated S1 has temporal and spectral characteristics similar to S1 recorded in humans and dogs. It also shows that the spectrogram cannot resolve the three components of the simulated S1. It is concluded that it is necessary to search for a better time-frequency representation technique for studying the time-frequency distribution of multicomponent signals such as the simulated S1.

Haemodynamic determinants of the mitral valve closure sound: A finite element study

“…These results are at odds with the only in vivo measurements that varied the ventricular pressure and processed the intra-ventricular S 1 with a non-stationary transform (CHEN and DURAND, 1997b). Part of the explanation for this discrepancy is that a simple amplitude scaling also increases the maxdP/dt.…”

Non Invasive Foetal Monitoring with a Combined ECG - PCG System

“…Despite the disadvantages mentioned above, FPCG provides valuable information about the physical state of the foetus during pregnancy and has the potential for detection of cardiac functionality anomalies, such as murmur, split effect, extra systole, bigeminal/trigeminal atrial. Such phenomena are not obtainable with the traditional CTG monitoring or other methods (Chen et al, 1997;Moghavvemi & Tan, 2003;Mittra et al, 2008).…”

Assessment of time–frequency representation techniques for thoracic sounds analysis

“…Hz, A 2 = 0.5, 2 = − , and k 2 = 60, as in [16]. The synthetic muscular component was modeled as a deterministic signal modulated both in amplitude and frequency by:…”

“…The first heart sound (S1) was simulated following the mathematical expressions proposed by Chen et al [16] based on the hypothesis that sound registered on the thorax at the heart apical area is composed by constant frequency vibrations due to the cardiac valves and by a frequency modulated vibration due to the myocardium. According to the valvular theory, S1 is considered as the response of the heart-thorax acoustic system to harmonic vibrations whose damping is due to blood and acoustic transmission across the thorax.…”

“…In other studies the selection was performed just by qualitative observations on the TF information as the reported for the analysis of S2 [15]. Also, the selection of the best TFR has been done by the inclusion of mathematical models of the analyzed sounds according to the physiological phenomenon involved in their genesis; Chen and Durand [16] reported results following the former approach.…”