You know the sound of your heartbeat: lub-dub, lub-dub. In some people, there's an extra noise that the blood makes as it flows through the heart. It sounds sort of like the noise of water flowing through a hose. This sound is called a murmur (say: mer-mer). Most murmurs don't mean anything is wrong. But sometimes they are a sign of a problem with the heart. The Heart and How It Works The heart is a strong muscle about the size of your fist that pumps blood around the body. It sits inside the chest and is protected by the rib cage. The heart has four different areas, or chambers. These chambers are connected to each other by valves that control how much blood enters each chamber at any one time. The valves open and shut with every beat. As the valves shut to control the flow of blood through the heart, they make the sound you recognize as your heartbeat. Depending on a person's age, the heart beats about 60 to 120 times every minute. Each heartbeat is really two separate sounds: lub-dub, lub-dub. Your heart goes "lub" with the closing of the valves that control blood flow from the upper chambers to the lower chambers. Then, as the valves controlling blood going out of the heart close, your heart goes "dub." What Is a Heart Murmur? A heart murmur is a whooshing sound between the beats that a doctor hears through a stethoscope. The whoosh is just an extra noise that the blood makes as it flows through the heart. Doctors usually discover murmurs during regular checkups or when kids see the doctor because they're sick. Just like kids, murmurs have grades. Grade 1 is the softest-sounding murmur, and Grade 6 is the loudest. A murmur graded 4, 5, or 6 is so loud you can actually feel a rumbling from it under the skin if you put your hand on the person's chest. What Happens If You Have a Murmur? More than half of all children have a heart murmur at some time in their lives and most heart murmurs don't mean anything is wrong. Doctors may call these "innocent", "functional," or "normal" murmurs. They are caused by blood rushing through the valves in a normal heart and are nothing to worry about. One common type of normal murmur is Still's murmur, named for the doctor who first described it. This murmur is most often heard in healthy children ages 3 to 7. A normal murmur can get louder when the blood flows faster through the heart, like when kids have a fever or run around. That's because an increase in body temperature or activity makes the heart pump more blood. When your temperature goes down, the murmur may get quieter or even disappear. It can be easier to hear heart murmurs in kids because they have less fat, muscle, and bone between the murmur and the doctor's stethoscope. Many normal murmurs become harder to hear as children grow older, and some eventually disappear. Even though most murmurs do not mean anything is wrong, sometimes a heart problem can cause a murmur. The heart may have a hole in it, a heart valve may leak, or a valve may not open all the way. If your doctor thinks your heart murmur could be due to a heart problem, you will need to see a pediatric cardiologist (say: pee-dee-ah-trik car-dee-ah-luh-jist). This kind of doctor knows a lot about children's hearts.