Due to blood flow (turbulence) murmurs are produced which can be systolic, diastolic or continuous. You should also note the position where they occur in the cardiac cycle
Heart murmurs are the sounds of turbulent blood flow in or around the heart. These swishing or whooshing sounds produce are audible on a stethoscope as lupp-dupp. Heart murmurs occur when heart fills with blood, blood leaves heart or throughout the cycle of filling and leaving of blood. Heart murmurs are harmless or abnormal. Harmless, or innocent, heart murmurs are associated with normal heart and do not need any treatment. It is common in fever, pregnancy, adolescence, exercise and conditions like anemia and hyperthyroidism. Abnormal murmurs are associated with congenital heart defects, congenital valve defects, septal defects, stenosis and cardiac shunts etc.