<P> In healthy adults , there are two normal heart sounds , often described as a lub and a dub ( or dup ) , that occur in sequence with each heartbeat . These are the first heart sound ( S ) and second heart sound ( S ) , produced by the closing of the atrioventricular valves and semilunar valves , respectively . In addition to these normal sounds , a variety of other sounds may be present including heart murmurs , adventitious sounds , and gallop rhythms S and S . </P>
when do you hear the lub and dub sounds of the heart
the closing of the atrioventricular valves and semilunar valves , respectively