Physicians listen to heart sounds for the purpose of diagnosing various cardiac malfunctions.
Within a cardiac cycle, there are four sounds produced by the mechanical activity of the heart. First heart sound is initiated by the onset of ventricular systole. It is the longest and loudest of the four sounds. S 1 is heard best over the apical region of the heart. S 1 is produced by the oscillation of blood in the ventricular chambers and vibration of the ventricular free wall.