A heart murmur is a noise heard between the beats of the heart. By listening to the heartbeat, doctors can usually classify the murmur by location and timing. Heart murmurs are extremely common, and almost always turn out to be harmless. Signs: A doctor will detect the heart murmur while listening to a baby's heart. Treatment: Normal or "innocent" heart murmurs usually don't require any treatment. If your child's pediatrician is concerned, though, he may refer you to a pediatric cardiologist for special tests.