Heart sounds are generally believed to be caused by acceleration and deceleration of blood in the cardiovascular system. Some theories proposed attribute the sounds directly to the opening and closing of the cardiac valves themselves. Regardless, some components of the heart sounds are ascribed to certain events in the cardiac cycle, such as the aortic and pulmonary components of the second sound. We are studying the possibilities of analyzing multichannel phonocardiogram (PCG) signals using passive sonar signal processing techniques, with the aim of locating the sources of the heart sound components in three dimensions. So far, we have been able to obtain only two-channel recordings of the PCG with an ECG channel with available equipment. Digital signal processing techniques have been developed for comparison of PCG segments by correlation methods. These techniques permit detection of similar PCG segments in the different channels which may be related to the same cardiac event. The time differences between such segments obtained from a number of PCG channels, along with the known locations of the PCG transducers, should aid source localization and ranging.
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