Difference Between Bell and Diaphragm of Stethoscope

By: | Updated: Oct-14, 2022
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The Bell and diaphragm of the stethoscope are the two important parts of a stethoscope. These parts are equally important to measure blood pressure and heart rate. The function of these parts can be better understood by studying the difference between them.

Summary Table

Bell of Stethoscope Diaphragm of Stethoscope
Smaller in shape. Bigger in shape.
Less available in the market. More widely available.
Captures low-frequency sound. Captures high-frequency sound.

Difference Between Bell and Diaphragm of Stethoscope


The diaphragm of a stethoscope refers to the huge, round pieces of metal attached to a chest piece, and are supposed to be placed on a patient’s skin to capture sound waves.

Meanwhile, the bell of the stethoscope refers to a small, round piece at the base of the stethoscope, and it appears to look a bit in the shape of a small bell.

Difference Between Bell and Diaphragm of Stethoscope

The main difference between the two parts is that the bell is usually fixed to the chest piece, while the diaphragm can be adjusted. The bell is usually made of plastic or metal.

It’s used to capture sound waves and transfer them to the earpiece, which helps doctors to determine the condition of a patient’s heart. The diaphragm, on the other hand, allows doctors to listen to different types of sound waves that can be easily distinguished.

The diaphragm has two main parts: a rim that fits over a chest piece and a central dome. The rim holds onto the chest piece while the central dome contains openings through which sound waves are transmitted to a person’s ear.

These openings are also known as “aural windows.” This part may also be made of metal or plastic material. In some cases, it may also include tubing to provide sound amplification. There are various designs and styles of this part depending on its purpose.

The stethoscope bell is used to help detect low-frequency sounds that can be hard to pick up with the large diaphragm. They can pick up sounds like heart murmurs very effectively. Because of the bells, doctors can easily pick up sounds that are hard to pinpoint.

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