A stethoscope is used to listen to sounds inside your body, primarily from your heart, lungs, blood vessels, and abdomen. This listening process, called auscultation, is one of the most fundamental tools in a physical exam. It lets a healthcare provider detect normal rhythms, pick up on subtle abnormalities, and decide whether further testing is needed.
Listening to Your Heart
The most familiar use of a stethoscope is checking your heart. A healthy heart produces two distinct sounds with each beat, often described as “lub-dub.” The first sound happens when the valves between your upper and lower heart chambers snap shut as the heart contracts. The second sound occurs when the valves leading to your lungs and the rest of your body close as the heart relaxes. Together, these two sounds confirm that your heart valves are opening and closing in the right sequence.
What clinicians are really listening for are sounds that shouldn’t be there. A heart murmur, for instance, is a whooshing or swishing noise caused by turbulent blood flow, often from a valve that’s too narrow or doesn’t close completely. Not all murmurs signal a problem (many are harmless, especially in children), but some point to valve disease that needs monitoring or treatment.
There are also extra heart sounds beyond the normal two. A third heart sound occurs during the relaxation phase when the lower chambers of the heart are stretched and stiff. In adults, this usually signals that the heart isn’t pumping effectively. In children and pregnant women, though, a third heart sound can be perfectly normal. A fourth heart sound happens when the upper chambers contract forcefully against a stiff lower chamber, and it’s almost always considered abnormal in adults. These subtle extras are difficult to hear without a stethoscope and years of training, but they carry significant diagnostic weight.
Checking Your Lungs
When a provider places a stethoscope on your back and asks you to take deep breaths, they’re mapping the airflow through your lungs and listening for sounds that indicate disease or obstruction. Normal breathing is relatively quiet. Abnormal sounds fall into a few distinct categories, each pointing to different problems.
Crackles (also called rales) are small clicking or bubbling sounds heard when you breathe in. They occur when air forces open small airways that have collapsed or filled with fluid, and they’re commonly associated with pneumonia, heart failure, or lung scarring. Wheezing is a high-pitched, almost musical sound heard mostly when you breathe out, caused by narrowed airways. It’s a hallmark of asthma and chronic bronchitis. Rhonchi sound more like snoring and result from mucus or other blockages in the larger airways, typical of bronchitis or other conditions that produce excess mucus.
Stridor is a particularly concerning sound: a harsh, wheeze-like noise that occurs when there’s a blockage in the windpipe or throat. Unlike wheezing, which originates deeper in the lungs, stridor usually indicates an upper airway problem. In children, it can signal croup; in adults, it may point to a foreign object or swelling that’s restricting airflow.
Detecting Blood Vessel Problems
A stethoscope can also reveal problems in your arteries. One important application is listening to the carotid arteries on either side of your neck. These vessels supply oxygen-rich blood to your brain, and when plaque builds up inside them, blood flow becomes turbulent and produces a whooshing sound called a bruit (pronounced “BROO-ee”), similar to water rushing through a fast-moving river.
Hearing a carotid bruit during a routine exam can be an early warning sign of plaque buildup, which raises the risk of a transient ischemic attack (a “mini-stroke”) or a full ischemic stroke. A bruit alone doesn’t reveal how much narrowing is present, so it typically prompts further imaging to assess the severity. It’s worth noting that some people with a bruit have no significant plaque and are otherwise healthy, while others with serious narrowing may not produce a bruit at all. Still, it’s a useful screening signal that costs nothing and takes seconds.
Providers also use stethoscopes to listen for bruits in other arteries, including those supplying the kidneys and legs, where narrowing can cause high blood pressure or poor circulation.
Evaluating Your Abdomen
Your intestines are constantly in motion, pushing food and liquid through your digestive tract. This creates gurgling and rumbling sounds that a stethoscope can pick up through your abdominal wall. Providers listen to these bowel sounds to assess whether your digestive system is working normally.
Reduced or absent bowel sounds suggest that intestinal activity has slowed, which can happen after surgery, with certain medications, or during serious conditions like a bowel obstruction or infection in the abdominal cavity. Hyperactive bowel sounds (louder and more frequent than normal, sometimes audible without a stethoscope) indicate increased intestinal activity. This can be as benign as hunger or diarrhea, or it can signal an early bowel obstruction where the intestines are working overtime to push contents past a blockage. Very high-pitched bowel sounds are particularly concerning, as they may be an early warning of obstruction before other symptoms become obvious.
Blood Pressure Measurement
If you’ve had your blood pressure taken manually (with an inflatable cuff rather than a digital machine), a stethoscope was part of the process. The provider inflates the cuff to temporarily stop blood flow in your upper arm, then slowly releases the pressure while listening with a stethoscope placed over the artery at your elbow. The first thumping sound they hear marks your systolic pressure (the higher number), and the point where the sound disappears marks your diastolic pressure (the lower number). This manual method remains one of the most accurate ways to measure blood pressure.
How Digital Stethoscopes Are Expanding the Tool
Traditional stethoscopes are acoustic instruments: sound travels through a hollow tube to the listener’s ears. Digital stethoscopes amplify body sounds electronically, which makes faint abnormalities easier to detect. Some models can record audio for later review or share it with a specialist remotely.
The more significant development is the addition of artificial intelligence. A study published in the Journal of the American Heart Association tested a deep learning algorithm paired with a digital stethoscope and found it could detect heart murmurs with 76% sensitivity and 91% specificity. When the algorithm focused on murmurs louder than the faintest grade, sensitivity jumped to 90%. For moderate-to-severe aortic stenosis (a common and dangerous valve condition), the system achieved 93% sensitivity. These tools don’t replace a provider’s judgment, but they can flag abnormalities that might otherwise go unnoticed, especially in settings where specialists aren’t readily available.
For all its simplicity, the stethoscope remains one of medicine’s most versatile diagnostic tools. In a matter of minutes, it gives a provider real-time information about your heart’s rhythm and valve function, your lung health, your vascular system, and your digestive activity, all without any radiation, needles, or waiting for lab results.