Stethoscope Bell vs. Diaphragm: What's the Difference?

The stethoscope is a crucial piece in any diagnostic toolkit, and it’s been that way for decades. If you’re like me, you’ll have used stethoscopes to listen to heartbeats, blood flow, and organ noises, depending on the patient.

However, do you know the main differences between the stethoscope bell and diaphragm?

In this guide, I’ll take you through the anatomy of a stethoscope and its main components and explore what separates the bell and diaphragm. Don’t start using one until you’ve read to the end!

Stethoscope Anatomy and Components 

Traditional stethoscopes consist of tubing, eartips, eartubes, and chest pieces. It’s in this chest piece where you’ll find the bell and the diaphragm, which are used to listen to different sound frequencies. Here’s a quick breakdown.

1. Bell 

The bell is the smaller, concave side of the chest piece, and it is used to listen for low-frequency sounds. That means it’s frequently used to listen for heart murmurs, bruits, and low frequencies emitted by the lungs. 

It’s typically used with children, older people, and smaller patients with thinner builds, and you use it delicately to pick up on very slight noises.

The bell can be vital in finding even slight anomalies in blood flow and organ noise. According to research, the bell is considered more sensitive than the diaphragm at assessing blood pressure:

“The study by Cushman et al. 29 of 48 men with histories of primary hypertension also reported that there was no significant SBP and DBP difference between the bell and the diaphragm. Our study demonstrated a tendency toward higher BP values with the bell in comparison with the diaphragm, with a significantly higher DBP.”

Liu et al.

2. Diaphragm

The diaphragm side of the chest piece is larger and typically picks up high-frequency sounds the body produces. For example, you’d use this side to listen to simple heartbeat and lung noises.

Typically, the diaphragm is designed for sounds that are easier to pick up, meaning you’d frequently use it by default when listening to patients. On many occasions, I switch sides or tune the diaphragm so that I can listen for less obvious noise.

Differences Between Bell and Diaphragm

The main differences between the bell and diaphragm are the sound frequencies they can pick up, their best use cases, pressure sensitivity and technique for use, and sound clarity and sensitivity.

Frequency Range

The diaphragm is used to pick up high-frequency sounds, such as heart murmurs, S1 and S2 heart sounds, and general bowel and lung sounds. The bell, meanwhile, picks up low-frequency sounds, such as vascular bruits and S3 and S4 heart sounds.

Best Use Cases (Adults vs. Pediatrics)

Generally, the bell, because it is smaller and easier to maneuver, is easiest to use when diagnosing children and infants, and patients with slender body types. For larger-build patients and most adults, the diaphragm is typically the first side to use for best results.

That said, there will be occasions when you may need to switch between both sides.

Pressure Sensitivity and Technique

The diaphragm only works so well when you apply firm pressure against the patient’s skin. For the bell, it’s the reverse! To pick up low-frequency sounds, you need to delicately place the bell side against the patient’s bare skin.

Proper Use and Techniques for Accurate Auscultation

Regardless of the patient, using stethoscope bells and diaphragms properly (i.e., by applying the right pressure, handling the stethoscope properly, positioning the patient, and knowing when to switch between bell and diaphragm smoothly) is vital for accurate diagnostics.

How Much Pressure to Apply

After consulting with the patient, start with either the bell or the diaphragm to listen for organ sounds. When starting with the bell, press lightly against the skin so that low-frequency sounds can be heard. You need to do the opposite for the diaphragm – press firmly.

Common Mistakes to Avoid

There are a few easy mistakes to make. For example, you may accidentally use the wrong side to listen for specific noises, might apply too much or too little pressure, or even end up using the chest piece on covered skin!

Always listen to bare skin and choose the side that applies best to the complaints your patient raise. For example, for bowel problems, you might use the bell for more subtle noises.

Patient Positioning Tips

To listen to patients effectively, you can position them either sitting up, supine, or left lateral recumbent (i.e., laying on their left side, horizontally). The position you sit your patient in will depend on what you are listening for. For example, regarding murmurs, many experts actually suggest using the left lateral decubitus position.

In most cases of listening to simple heart sounds, doctors and nurses sit patients upright and apply to the chest.

Switching Between Bell and Diaphragm Smoothly

In most cases, you’ll be able to gently rotate the chestpiece and click the new side into place. In some cases, however, you may wish to start listening via the diaphragm, then gently switch to the bell to pick up more sensitive sounds. Some advanced tools, such as some Littmann stethoscopes, let you adjust frequency pickup with just one side!

Choosing the Right Stethoscope for Your Needs

There are several types of stethoscopes for different diagnostic needs and purposes. For example, single vs. dual head stethoscopes differ in sensitivity, tunable diaphragms allow for more accurate auscultation, and digital stethoscopes help to improve the diagnostic process.

Single Head vs. Dual Head Stethoscopes

Single head stethoscopes are very common and are recommended for general listening. However, dual head types offer more sensitivity, making them ideal for close bell auscultation. These stethoscopes deliver noise through two individual ear channels.

Tunable Diaphragms

Tunable diaphragms remove the need to switch between two sides of a chest piece. Specifically, these tools allow you to vary pressure to listen for certain frequencies.

Digital and Electronic Stethoscopes

Digital and electronic stethoscopes can amplify the sounds you hear during auscultation and allow you to delicately adjust your listening technique. There is less pressure required for you to switch between the bell and the diaphragm intensively, because you pick up a much higher sound quality all-around.

Specialty-Specific Recommendations

There are several specialised stethoscopes designed to listen for certain sounds and issues. For example, some are designed to listen for subtle heart sounds, while others are designed for pediatric diagnostics. Regardless of the tool used, the bell and diaphragm technique still applies.

Technological Advancements in Stethoscope Design

Stethoscope design advancements, such as electronic sound amplification, Bluetooth and digital recording features, AI-based diagnostic support, and telemedicine-ready stethoscopes, have greatly improved the quality of sound and accuracy of diagnostics.

Electronic Sound Amplification

ESA technology helps users to listen more carefully to their patients. Amplification effectively improves the diagnoser’s chances of hearing diagnostic tells, which they would usually rely on using the bell for with acoustic stethoscopes. ESA stethoscopes haven’t replaced traditional tools outright, but have enhanced the listening and diagnostic process.

Bluetooth and Digital Recording Features

Digital recording and capture via Bluetooth helps diagnosers to capture listening data for reference later on. That means they don’t have to intensively listen to a patient and switch between the bell and diaphragm in real-time. They can listen to the audio later and analyse more closely.

AI-Based Diagnostic Support

Emerging stethoscope technology uses artificial intelligence to carefully analyse and match noises recorded through digital stethoscopes. That means AI can effectively pre-diagnose patients and raise anomalies that users might miss on first listen.

Telemedicine-Ready Stethoscopes

Telemedicine stethoscopes can be used in distanced diagnosis, meaning medical professionals can listen to patients from afar. Data from the patient is delivered to doctors or nurses via telemedicine, allowing for remote analysis without the need for the patient to travel.

Frequently Asked Questions

Let’s close with some common questions about bells and diaphragms.

Can I use the diaphragm for all types of sounds?

No – stethoscope diaphragms are typically used to listen for high-frequency sounds, and aren’t designed for low-frequency noises.

Is the bell still used with modern stethoscopes?

Yes, the bell is still highly useful in diagnosing low-frequency sounds through modern stethoscopes. In particular, they are still used widely in pediatrics and gerontology.

How do I know which side I'm using?

The smaller, cup-shaped side of the stethoscope chest piece is the bell, which is for low-frequency sounds. The larger, flatter side of the chest piece, meanwhile, is for high-frequency sounds.

Do all stethoscopes have both bell and diaphragm?

No – some stethoscopes have single, tunable diaphragms that remove the need to switch sides during auscultation.

Final Thoughts

It’s always important to learn how to use a stethoscope before you dive right in! Thankfully, I speak from experience when I say that it won’t usually take long for you to get to grips with how the bell and diaphragm work in practice.

 

Sources

Best stethoscopes: Littmann stethoscopes, Prestige, Spirit and more. (n.d.). Medshop Australia. Retrieved September 15, 2025, from https://www.medshop.com.au/collections/stethoscopes

How to use a stethoscope effectively: Comprehensive guide. (n.d.). Medshop Australia. Retrieved September 15, 2025, from https://www.medshop.com.au/blogs/news/how-to-use-a-stethoscope-effectively-comprehensive-guide

Littmann stethoscopes best sellers. (n.d.). Medshop Australia. Retrieved September 15, 2025, from https://www.medshop.com.au/collections/littmann-stethoscopes

Liu, C., Griffiths, C., Murray, A., & Zheng, D. (2016). Comparison of stethoscope bell and diaphragm, and of stethoscope tube length, for clinical blood pressure measurement. Blood Pressure Monitoring, 21(3), 178–183. https://doi.org/10.1097/MBP.0000000000000175

Techniques - Heart sounds & murmurs exam - Physical diagnosis skills - University of Washington School of Medicine. (n.d.). University of Washington School of Medicine. Retrieved September 15, 2025, from https://depts.washington.edu/physdx/heart/tech.html

Ultimate guide to different types of stethoscopes. (n.d.). Medshop Australia. Retrieved September 15, 2025, from https://www.medshop.com.au/blogs/news/ultimate-guide-to-different-types-of-stethoscopes