The sounds are caused by the vibrations created by the closing of the heart valves, of which there are two in the normal situation: the first when the atrioventricular (tricuspid and mitral) valves close at the beginning of systole and the second when the aortic and pulmonary valves (the semilunar valves) are closed at the end of systole. It allows detecting inaudible sounds and heart murmurs, and permanently recording these sounds. By contrast, a regular stethoscope cannot always detect all of these sounds or heart murmurs, and provides no record of their occurrence. This device provides the ability to estimate and record heart sounds that give the treating physician information not readily available with more sophisticated tests, and provide vital information about the effects of certain medications on the heart. It is also an effective way to track the progress of a person's disease. [Need a medical source].