Listening to heart sounds requires a stethoscope, a quiet room, and knowledge of four specific spots on the chest where different valves are best heard. The technique is straightforward once you understand what you’re listening for: two main sounds per heartbeat, their rhythm, and anything extra between them.
The Four Listening Points
Your heart sits behind your sternum (breastbone) and ribs, angled slightly to the left. Different valves sit closer to different parts of the chest wall, so you move the stethoscope to four standard locations to isolate each one. These are named after the valves, not because the valve is directly underneath, but because sound from that valve travels best to that spot.
- Aortic area: second intercostal space (the gap between your second and third ribs) at the right edge of the sternum. This puts the stethoscope as close as possible to the proximal aorta.
- Pulmonic area: second intercostal space at the left edge of the sternum, directly over the pulmonary artery.
- Tricuspid area: third and fourth intercostal spaces along the lower left sternal border, over the right ventricle.
- Mitral area: fourth and fifth intercostal space in the midclavicular line (roughly in line with the middle of your collarbone), at the apex of the heart. This is the closest point to the left ventricle.
To find the intercostal spaces, start by locating the bony ridge where your second rib meets the sternum. The gap just below that rib is the second intercostal space. Count downward from there.
What Normal Heart Sounds Are
A healthy heartbeat produces two distinct sounds, often described as “lub-dub.” The first sound (S1) is the “lub.” It happens when the mitral and tricuspid valves snap shut at the start of each contraction, preventing blood from flowing backward into the upper chambers. S1 is loudest at the apex, the mitral listening point.
The second sound (S2) is the “dub.” It occurs when the aortic and pulmonic valves close after the ventricles finish pumping. S2 is actually two components very close together: aortic valve closure, which is louder and heard across the entire chest, and pulmonic valve closure, which is softer and confined to the upper left sternal border. Most of the time these two components sound like a single crisp sound. During a deep breath in, they can separate slightly, creating what’s called physiological splitting. This is normal. It happens because inspiration draws more blood into the right side of the heart, delaying pulmonic valve closure, while the aortic valve closes a bit earlier. Together, those two shifts account for the audible split.
Using the Bell vs. the Diaphragm
Most stethoscopes have two sides on the chest piece. The flat, wider side is the diaphragm, which filters out low-frequency vibrations and highlights higher-pitched sounds. The smaller, concave side is the bell, which picks up low-frequency sounds more effectively by producing a louder output in that range.
Use the diaphragm for most of your exam. S1, S2, and many murmurs fall in the higher-frequency range. The soft but high-pitched early diastolic murmur of aortic regurgitation, for instance, is best caught with the diaphragm pressed firmly against the skin. Switch to the bell when you’re specifically listening for low-pitched sounds like the third heart sound (S3) or the rumble of mitral stenosis. Apply the bell lightly; pressing too hard stretches the underlying skin into a makeshift diaphragm and filters out the very low tones you’re trying to hear.
Patient Positioning and Technique
Start with the person lying on their back (supine) in a quiet room. Ambient noise is one of the biggest barriers to hearing subtle sounds, so turn off televisions, close doors, and wait for conversation to stop. Place the stethoscope directly on skin, not over clothing.
Three positions cover nearly everything you need:
- Supine: your starting position. Listen systematically through all four valve areas.
- Left lateral decubitus: the person rolls onto their left side. This shifts the heart’s apex closer to the chest wall and makes the low-frequency rumble of mitral stenosis and the S3 gallop much easier to detect. Use the bell at the apex in this position.
- Sitting up, leaning forward: brings the base of the heart closer to the anterior chest wall. This is the best position for hearing the soft, blowing murmur of aortic regurgitation. Ask the person to exhale and hold their breath briefly while you listen with the diaphragm at the left sternal border.
Breathing affects what you hear. Right-sided heart sounds generally get louder during inspiration because more blood returns to the right heart. Left-sided sounds tend to be louder during expiration. You can use this to your advantage: if you’re trying to decide whether a murmur originates on the right or left side, ask the person to breathe in slowly and listen for a change in volume.
Listening Systematically
The most common mistake is skipping around or listening too briefly. Spend at least one full respiratory cycle (a breath in and a breath out) at each location. Many clinicians move through the four points in order, from the aortic area down to the mitral area, though the direction matters less than being consistent so you don’t miss a spot.
At each location, focus on one thing at a time. First, identify S1 and S2 and their rhythm. Then listen to the space between S1 and S2 (systole). Then listen to the space between S2 and the next S1 (diastole). Extra sounds or murmurs hide in these gaps, and you’re more likely to catch them when you actively concentrate on one interval rather than trying to absorb everything at once.
Extra Sounds: S3 and S4
Beyond the normal two-sound rhythm, you may hear a third or fourth heart sound. Both are low-pitched and best detected with the bell at the apex while the person lies in the left lateral decubitus position.
S3 occurs in early diastole, right after S2, producing a “lub-dub-ta” rhythm sometimes called a ventricular gallop. In children and adults under about 35 to 40, an S3 is often normal. After age 40, it typically signals that the ventricle isn’t pumping efficiently or is overloaded with volume. Conditions like heart failure, significant valve leakage, and severe anemia can produce it. An S3 in an older adult is considered one of the most sensitive physical exam findings for ventricular dysfunction.
S4 occurs just before S1, creating a “ta-lub-dub” rhythm called an atrial gallop. It happens when the atria contract forcefully against a stiff or thickened ventricle. It is almost always abnormal in adults and often points to conditions that make the heart muscle less compliant, such as long-standing high blood pressure or coronary artery disease.
Recognizing and Grading Murmurs
Murmurs are whooshing or blowing sounds caused by turbulent blood flow through or near the heart valves. Not all murmurs indicate disease. Many young, healthy people have quiet “flow murmurs” that carry no clinical significance.
When you hear a murmur, note its timing (systolic or diastolic), its location, and its intensity. Intensity is graded on a six-point scale:
- Grade 1: faint, barely audible even in a quiet room
- Grade 2: soft but clearly heard
- Grade 3: easily audible, no vibration felt on the chest
- Grade 4: easily audible with a palpable vibration (called a thrill) felt under your hand
- Grade 5: loud enough to hear with the stethoscope barely touching the chest, thrill present
- Grade 6: audible with the stethoscope lifted off the chest entirely
Grades 1 and 2 systolic murmurs are common and frequently benign. Any diastolic murmur, or a systolic murmur grade 3 or above, generally warrants further evaluation with imaging.
Practicing Effectively
Cardiac auscultation is a skill built through repetition. Listen to as many normal hearts as you can before focusing on pathology, because your ability to spot something abnormal depends entirely on how well you know what normal sounds like. Practice on friends, family members, or classmates in a quiet setting. Online simulation tools from medical schools, including freely available audio libraries, let you compare normal and abnormal recordings side by side and train your ear for subtle findings like a faint S3 or a grade 1 murmur.
Speed comes with experience. In the beginning, expect to spend a full minute or more at each listening point. Over time, you’ll recognize patterns within seconds and focus your extended listening where something catches your attention.