A heart murmur is an unusual sound heard during a heartbeat, often described as a whooshing or swishing noise. It occurs when blood flows through the heart's chambers or valves in a turbulent manner. Heart murmurs can be classified as either innocent (harmless) or abnormal, depending on their cause and associated symptoms. Innocent murmurs are common in children and usually resolve on their own without treatment. Abnormal murmurs may indicate underlying heart conditions, such as valve problems or congenital heart defects. A healthcare professional can evaluate murmurs through a physical examination and may recommend further tests if necessary.