We have discussed all the four heart sound with normal and abnormal characteristics. A. First heart Sound (S1) : I. Description : The First Heartbeat (S1) The shutting of the mitral and tricuspid valves causes the first heart sound. The sound produced by the mitral valve closing is known as M1, while the sound produced … Continue reading All types of heart sounds – S1, S2, S3, and S4 | Normal and Abnormal characteristics