What Do Doctors Hear When They Use A Stethoscope?

If you’ve ever wondered what doctors actually hear when they plug the ear tips of a stethoscope in, you’re definitely not alone.
Many people find stethoscopes as very symbolic and fascinating pieces of equipment, yet they have no clue what doctors really hear or look for when they place the chest piece on a patient’s chest.
If you’ll be completely honest with yourself, you’ve probably handled a stethoscope, perhaps when you were a child, placed the ear tips in your ears and put the sensitive surface on your chest to listen to your heart. What you likely heard was the famous ‘lub dub’ sound symbolic of the sounds that emanate from the heart each time it beats.
Now, truth be told, doctors don’t only listen to heart sounds. As a matter of fact, there’s so much to hear when you use a stethoscope.
In this post, I’ll try to tell you various sounds doctors are trained to pick when using a stethoscope. I’ll also try to explain what those sounds mean about the patient.

1. Normal Heart Sounds

We’ll start with the most common sound that is easiest to pick with a stethoscope. When the chest piece is placed on the left lower side of a patient’s chest, what you hear is the characteristic ‘lub dub’ sound. Now, that means that the heart is going through the normal pumping cycle. The heart’s pumping cycle is divided into two: diastole and systole.
During systole, the heart contracts, forcefully closing two of the four valves in the heart. This is the first ‘lub’ sound you hear, it is medically called the S1.

During diastole, the heart relaxes, taking in blood from the body’s circulation, and in the process, the two other valves close, causing the second ‘dub’ sound. This sound is medically called the S2.

2. Normal Breath Sounds

When you take in air and exhale it, your body uses the oxygen in the air to sustain its cells and tissues. Because respiration is very vital to life, doctors must be able to tell if there’s anything wrong with a person’s breathing, and they do this many times by using a stethoscope.
What we hear when someone is breathing normally sounds soft and low pitch, like air filling up a sac.

3. Blood Pressure Korotkoff Sounds

Now, the word ‘korotkoff’ may sound strange to you but is very normal and surprisingly easy to pronounce by a medical student or doctor.
They are the sounds the arteries make when a good stethoscope is used to check a person’s blood pressure manually.
I know that the use of a digital stethoscope and blood pressure monitors today is on the rise, but when a manual mercury sphygmomanometer is used with a stethoscope, you hear korotkoff sounds.
Let me explain how it works:
When the stethoscope is rightly placed on the junction between a patient’s arm and forearm, and the cuff of the manual sphygmomanometer is inflated, the mercury level in the blood pressure gauge rises. When a doctor has inflated to a level higher than the blood pressure estimate, the pressure is released.
At this point, the doctor watches the gauge carefully while dropping the cuff pressure gradually. What he’s actually listening for are tapping sounds. These are korotkoff sounds.
The moment the first tapping sound is heard, the blood pressure reading is the systolic blood pressure.
As the cuff pressure is continuously lowered, the tapping sounds will disappear. The blood pressure reading when these sounds disappear is called the diastolic blood pressure.

Note: In case you’re confused what systolic and diastolic blood pressures mean, here’s an explanation for you. Blood pressure is usually read as two numbers.
Something like this: 120/80 mmHg.
The first and higher figure is the systolic blood pressure, that is the blood pressure when the heart contracts.
The second and lower figure is the diastolic blood pressure, that is the blood pressure when the heart muscle relaxes.

4. Bowel Sounds

If you’ve had a serious abdominal problem before like severe diarrhea or constipation, you may have seen your doctor place a stethoscope on your abdomen. You might have wondered if he was making a mistake or what on earth he was looking for there with a stethoscope.
But the truth is that he’s simply on the lookout for bowel sounds– the sounds your intestines make when they pass food around. Sometimes, they can be overactive like when you have diarrhea or sometimes they can be a bit silent, like when you’re asleep.


So, we’ve been able to go through four common sounds doctors look out for when they use a stethoscope. This isn’t a list of all the possible sounds that can be heard, rather I chose to discuss the ones you could relate to- the normal sounds.
Sometimes there are abnormal sounds that can be heard and may suggest a problem, but that may be a bit too complex.
Nevertheless, I hope you were able to learn something from this post so you can tell your doctor next time you meet, that you now know what is heard when a stethoscope is used.

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