Doctors listen to your heart to check whether your valves are opening and closing properly, whether your heart rhythm is normal, and whether any unusual sounds suggest an underlying problem. It’s one of the quickest, most informative parts of a physical exam, and the sounds your heart makes can reveal conditions ranging from harmless quirks to serious valve disease.
What Your Heart Sounds Like Normally
A healthy heart produces two distinct sounds with each beat, often described as “lub-dub.” The first sound happens when the valves between the upper and lower chambers of your heart snap shut as the heart contracts to push blood out. The second sound comes from a different pair of valves closing when the heart relaxes between beats, preventing blood from flowing backward out of the major arteries.
These two sounds are the baseline. Your doctor is listening for their timing, their loudness, and whether anything extra shows up between or alongside them. A normal heart sounds crisp and rhythmic, with a predictable pause between each pair of sounds. Any deviation from that pattern tells a story.
Why They Move the Stethoscope Around
Your heart has four valves, and each one is best heard at a specific spot on your chest. That’s why your doctor doesn’t just press the stethoscope in one place and call it done. They typically listen at four or five locations, starting near the center of your breastbone and working outward.
The aortic valve is heard best on the right side of your breastbone near your second rib. The pulmonary valve is in the same position on the left side. Moving down the left edge of the breastbone, the tricuspid valve comes through most clearly around the fourth rib space. And the mitral valve is heard at the bottom tip of the heart, out toward the left side of your chest roughly below the middle of your collarbone. By listening at each spot, your doctor can isolate the sounds of individual valves and pinpoint which one might be causing trouble.
They may also ask you to roll onto your left side or sit up and lean forward. These positions bring certain parts of the heart closer to the chest wall, making faint or subtle sounds easier to detect.
What a Murmur Means
A heart murmur is an extra whooshing or swishing sound between the normal “lub” and “dub.” It’s caused by turbulent blood flow, usually because a valve isn’t working perfectly. Murmurs fall into two broad categories based on when they occur in the heartbeat cycle.
If the extra sound happens while the heart is contracting (between the first and second sounds), it could indicate a narrowed valve that blood is being forced through, or a leaky valve that’s allowing blood to flow backward. A classic example is a narrowed aortic valve, which produces a characteristic rising-and-falling whoosh heard near the upper right chest that can sometimes radiate up toward the neck.
Murmurs that occur while the heart is relaxing tend to signal different problems. A leaky aortic valve lets blood slip back into the heart, creating a soft blowing sound. A narrowed mitral valve forces blood through a tight opening, producing a low rumble heard near the bottom of the heart. Some of these conditions develop from wear and tear over decades, while others trace back to infections, congenital defects, or the lingering effects of rheumatic fever.
Not all murmurs are dangerous. Many are “innocent” or “functional,” meaning they produce a sound but don’t reflect any structural problem. These are especially common in children and young adults. Your doctor judges a murmur by its loudness, its timing, where it’s heard loudest, and whether you have any other symptoms.
Extra Sounds Beyond Murmurs
Beyond the standard two heart sounds and murmurs, doctors also listen for a third or fourth sound. A third heart sound is a low, quiet thud that occurs right after the normal second sound, during the phase when the lower chambers of the heart are filling with blood. In children and adults under about 40, this can be completely normal. After 40, it’s usually a red flag. It’s considered the most sensitive indicator of a weakened or overloaded heart muscle, and it can point to conditions like heart failure, severe valve leakage, or problems caused by long-standing high blood pressure.
A fourth heart sound occurs just before the first normal sound and suggests the heart muscle has become stiff. This is more common in older adults, particularly those with thickened heart walls from years of high blood pressure or coronary artery disease. Doctors may also listen for rubbing sounds that suggest inflammation of the sac surrounding the heart, or unusual clicking noises that can indicate a valve that bulges slightly with each beat.
How the Stethoscope Itself Works
Most stethoscopes have two sides to the chest piece: a flat, wide disc called the diaphragm and a smaller, open cup called the bell. The diaphragm picks up higher-pitched sounds better, while the bell emphasizes lower-pitched ones. Since many abnormal heart sounds (like a third heart sound or the rumble of a narrowed mitral valve) are low in frequency, your doctor may flip between the two sides depending on what they’re trying to hear.
Heart sounds are quiet in general, with most of the important acoustic information sitting near the lower edge of what human ears can detect. This is part of why a noisy exam room or a rushed listen can cause subtle findings to be missed.
How Accurate Listening Alone Really Is
Listening with a stethoscope is a screening tool, not a definitive diagnostic test. A large systematic review of studies on the accuracy of heart auscultation found that sensitivity for detecting valve disease varied enormously, from as low as 16% to as high as 91% depending on the condition and the examiner’s skill level. Some conditions are easier to catch than others. Aortic stenosis (a narrowed aortic valve) is detected by stethoscope with sensitivity between 72% and 97%, making it one of the most reliably caught valve problems. Mitral regurgitation (a leaky mitral valve) is harder to pin down, with detection rates ranging from 30% to 100%.
The takeaway from the research is that a stethoscope exam is valuable as a first pass. If your doctor hears something abnormal, the next step is typically an echocardiogram, which is an ultrasound of the heart that can show the valves in motion and measure exactly how well they’re functioning. But the stethoscope remains the reason most valve problems get flagged in the first place, often during a routine checkup when you came in for something unrelated.
Breathing and Movement Tricks
Your doctor may ask you to breathe deeply, hold your breath, or bear down as if straining. These aren’t random requests. Breathing in deeply increases blood flow to the right side of the heart, which makes right-sided valve problems louder and easier to identify. Bearing down (the Valsalva maneuver) temporarily reduces the amount of blood returning to the heart, which changes the loudness and character of certain murmurs in ways that help your doctor distinguish one condition from another.
These simple maneuvers can turn an ambiguous sound into a clear finding, helping your doctor decide whether what they’re hearing is something to investigate further or something benign.
What Happens if Something Sounds Off
If your doctor detects an unusual sound, the response depends on context. A soft murmur in a healthy young person with no symptoms often requires nothing more than a note in your chart and monitoring over time. A new murmur in an older adult, or any murmur accompanied by symptoms like shortness of breath, chest pain, dizziness, or swelling in the legs, will typically prompt an echocardiogram for a closer look.
In many cases, what your doctor hears through the stethoscope is completely normal. The exam takes less than a minute, it’s painless, and it provides a surprising amount of information about how well the most important muscle in your body is doing its job.