Looking back, I must have been very naive as a medical student as I thought sophisticated technology powered the stethoscope. I still get questions on how a stethoscope works, sometimes from patients who are doubtful about the ability of the device to actually help the doctors. If you are one of those people who want to know how this seemingly simple medical device actually works, read on.
First, let us understand what a stethoscope is:
At its most basic, a stethoscope is nothing more than a funnel that amplifies sound waves and directs them to the user’s ears. It was first invented in 1816 by French physician René Laennec. Initially, he rolled a sheet of paper into a cone shape and placed it against his patient’s chests to listen to their heartbeat. In 1819, Renee Laennec wrote a seminal paper on ‘indirect body listening device’ that formed the basis of incorporating physical examination into patients’ autopsies in diagnosis.
Below is an image of a stethoscope with all parts labeled.
The stethoscope that we use today is a lot more sophisticated, but the basic principle remains the same. It is still a funnel that amplifies sound waves and directs them to the user’s ears.
Parts of a stethoscope:
- 1. Headset: The headset of a stethoscope has hollow ear tubes which measure 15.24 centimeters in length. It is composed of two earpieces and tubing. The tubing joins the earpieces to the chest piece. The earpieces fit snugly into your ears, and you can use them to adjust the tension on the tubing. This tension determines how far apart the earpieces will sit on your head.
- 2. soft-sealing ear tips: Most stethoscopes come with two types of ear tips—hard plastic and soft silicone. The hard plastic ear tips provide a better seal, which is important when you’re trying to hear faint sounds. But they can be uncomfortable to wear for long periods of time. The silicone ear tips are more comfortable but don’t provide as good of a seal.
- 3. Chestpiece: The chest piece is the most important part of the stethoscope. It consists of two sides—the diaphragm and the bell. The diaphragm is used to hear high-pitched sounds, such as the heart and lungs.
- The bell is used to hear low-pitched sounds, such as the intestines.
- 4. Tubing: The tubing is the part of the stethoscope that connects the chest piece to the headset. It’s typically made of latex or PVC. Latex is more flexible but can cause allergic reactions in some people. PVC is less flexible but doesn’t cause allergies.
- 5. Binaural assembly: The binaural assembly is the part of the stethoscope that connects the tubing to the earpieces. It includes a metal or plastic piece called the yoke, which connects the two tubes, and two earpieces.
How does a stethoscope work?
Now let us understand how it works:
1) The bell of the stethoscope is placed on the patient’s skin.
2) The user then listens through the earpieces for sound waves generated by the patient’s body.
3) These sound waves travel through the tubing and are amplified by the chest piece.
4) The diaphragm of the chest piece vibrates in response to the sound waves, which creates new sound waves.
5) These new sound waves travel through the tubing and are amplified by the earpieces.
6) The user hears the amplified sound waves through the earpieces.
Video Explanation of how a stethoscope works;
Q: How often should I clean my stethoscope?
A: You should clean your stethoscope after every use. Use a mild soap and warm water to clean the chest piece and earpieces. Rinse the parts well and dry them with a lint-free cloth. You can also use an alcohol-based disinfectant to clean the chest.
Q: What is auscultation?
A: Auscultation is the act of listening to internal body sounds, such as the heart, lungs, and intestines, with a stethoscope. Auscultation can be used to diagnose a variety of conditions, such as heart murmurs, lung diseases, and intestinal block’s.