Heart Sounds and Stethoscopes

Abstract

Heart sounds are the acoustic vibrations produced during the systole and diastole of the cardiac cycle. The art of evaluating the acoustic properties of heart sounds is known as heart auscultation. Heart auscultation has long been the most common technique for assessing the cardiac function of a patient. Conventional medical practice uses a mechanical stethoscope for auscultation. Often, the practitioners would need to rely on their hearing ability and their subjective judgement on the interpretation of the sounds. With the introduction of electronic stethoscopes, people are now hoping to measure and analyze heart sounds in a more objective manner. The rapid development in microchip technology in the past decade has resulted in electronic stethoscopes that are portable, robust to noise, and convenient to use. The future trend of electronic stethoscope would be a multifunctional auscultatory device with graphical display, wireless data transmission, real‐time signal processing for noise removal, selectable frequency response, etc. The newly developed electronic stethoscopes allow heart sounds to be digitally recorded and downloaded to a computer for analysis. Many of the computer‐based heart sound analysis techniques adopted by researchers, for example, wavelet transform and neural network, have already provided new insight into the diagnostic value of heart sound. The exploration of further techniques in the coming years would hopefully help to realize the full potential of heart sound auscultation as a tool the early detection of heart diseases.

Automatic phonocardiogram segmentation using the Sliding Window Autocorrelation algorithm

“…The contraction of muscle tissue allows blood to be pumped through the heart [71]. Typically, as seen in Figure 1.2, oxygenated blood from the lungs is received by the LA, pumped by the LA through the mitral valve to the LV, pumped by the LV through the aortic valve to the aorta, and circulated to the body where the oxygen will be used.…”

“…According to [50], blood flow changes and valve vibrations are associated with cardiac sounds heard during the cardiac cycle. According to [71], audible sounds are produced from the opening and closing of heart valves, the flow of blood in the heart, and the vibration of heart muscles.…”

“…Murmurs are typically associated with heart valve pathology, such as stenosis and insufficiency [50] [71]. Heart valve stenosis (or narrowing) refers to when a heart valve does not open fully (e.g.…”