Innocent heart murmurs are sounds made by the blood circulating through the heart's chambers and valves or through blood vessels near the heart.
Innocent murmurs are common in children and are quite harmless.
In fact, they're so common that in any group of children, a large percentage is likely to have had one at some time. Innocent murmurs also may disappear and then reappear. Most innocent murmurs disappear when a child reaches adulthood, but some adults still have them. When a child's heart rate changes, such as during excitement or fear, the innocent murmurs may become louder or softer. This still doesn't mean that the murmur is abnormal.