Stethoscope Parts Explained: Bell, Diaphragm, Tubing and What They Do

Every stethoscope, from a student's first to a consultant cardiologist's go-to, is built from the same core stethoscope parts: earpieces, ear tubes, tubing, a stem, and a chestpiece containing a bell and diaphragm. Each component plays a specific role in carrying sound from the patient's body to the clinician's ears. Understanding what these parts do (and what separates a good stethoscope from a great one) helps you choose the right instrument, maintain it properly, and get the most out of every auscultation.

Below, we walk through each part in detail, explain the difference between the stethoscope bell vs diaphragm, and highlight the engineering that makes Littmann stethoscopes the benchmark for acoustic performance.

Stethoscope parts: labelled diagram

Before diving into the detail, here is a quick visual overview of the six core parts and where they sit on the instrument.

In this article

• Ear tips (earpieces)
• Ear tubes (binaural)
• Tubing
• The stem
• The chestpiece: bell vs diaphragm
• Chestpiece construction: stainless steel vs aluminium
• What makes Littmann stethoscope parts different?
• Quick-reference parts table
• Which Littmann is right for you?
• FAQ

What do the ear tips do?

Ear tips (sometimes called earpieces) are the small silicone or rubber buds that sit inside your ear canals. Their job is straightforward but critical: they form an airtight seal so that sound travels cleanly from the tubing into your ears without leaking or letting ambient ward noise in.

Most stethoscopes ship with two or three sizes. A proper fit matters more than people realise. Loose ear tips let sound escape, making faint murmurs and quiet breath sounds harder to detect. Littmann stethoscopes use soft-sealing ear tips designed to conform to the shape of your ear canal, reducing ambient noise and improving comfort during long shifts.

Soft-seal vs snap-tight ear tips

There are two main ear tip styles. Soft-seal tips (used on all current Littmann models) are made from pliable silicone that moulds gently to the ear canal. They create a better acoustic seal and are more comfortable for extended wear. Snap-tight tips are firmer, typically rubber, and click into the ear tube rather than sliding on. They are common on older or budget stethoscopes and tend to let more ambient noise through.

How to check your ear tip fit

Put the stethoscope on and lightly tap the diaphragm. If the sound is clear and ward background noise drops noticeably, the seal is good. If the tapping sounds hollow or you can still hear conversations clearly, try the next size up. Most Littmann kits include both small and large soft-seal tips, so it is worth trying both.

Maintenance tip: Wipe your ear tips with an alcohol swab after each use. Replace them when they become hard, cracked, or no longer form a snug seal. For daily users, that typically means every 6 to 12 months.

What are ear tubes and why do they matter?

The ear tubes (also called the binaural) are the two metal arms that connect the ear tips to the top of the tubing. They are usually made from stainless steel or aluminium, joined by a tension spring that lets you adjust how tightly they sit against your head.

The angle of the ear tubes is important. They should point slightly forward, following the natural angle of your ear canals. If they point straight or backwards, sound transmission drops and comfort suffers. Littmann stethoscopes feature an anatomically designed headset with ear tubes angled to match the average ear canal, so you get optimal sound delivery right out of the box.

How does stethoscope tubing affect sound quality?

The tubing is the flexible tube that runs from the chestpiece up to the ear tubes. It carries acoustic vibrations from the patient's body to your ears, and its material, thickness, and design all influence what you hear.

There are two main designs:

• Single-lumen tubing: One channel inside a single tube. Simpler and lighter, used on many entry-level stethoscopes including the Littmann Classic III.
• Dual-lumen tubing: Two separate channels moulded into what looks like a single tube. This provides a dedicated sound path for each ear, improving stereo separation and acoustic clarity. The Littmann Cardiology IV uses this design.

Traditional dual-tube stethoscopes (with two visibly separate tubes) often produce a rubbing noise when the tubes touch. Littmann's dual-lumen design solves this by housing both channels inside one outer tube, eliminating that interference entirely.

Littmann also uses Next Generation tubing across its range. This material resists skin oils, alcohol, and staining far better than standard PVC, meaning the tubing stays supple and does not crack or discolour as quickly. It is also free from natural rubber latex and phthalate plasticisers, making it suitable for clinicians and patients with latex sensitivities.

What is the stem on a stethoscope?

The stem is the short metal connector between the tubing and the chestpiece. On a dual-sided stethoscope, the stem contains a valve mechanism that lets you rotate between the diaphragm side and the bell side. You will usually hear or feel a click when the active side switches.

On Littmann stethoscopes, the stem uses a recessed selector spline. This creates a smoother profile (no protruding parts to catch on clothing) and provides a clear visual indicator showing which side of the chestpiece is currently active. It is a small detail, but it saves time during examinations and avoids the common mistake of listening through the wrong side.

Stethoscope bell vs diaphragm: what is the difference?

The chestpiece is the business end of the stethoscope, the part placed against the patient. Most clinical stethoscopes have a dual-sided chestpiece with two distinct components: the diaphragm and the bell.

The diaphragm

The diaphragm is the larger, flat side of the chestpiece. It is covered by a thin, taut membrane (usually plastic or epoxy/fibreglass) that vibrates when it contacts the skin. These vibrations are transmitted as sound waves through the tubing to your ears.

The diaphragm is best for detecting high-frequency sounds, including normal breath sounds, bowel sounds, and most heart sounds (S1 and S2). Because of its larger surface area, it picks up a wider range of acoustic information and is the side most clinicians use for the majority of their assessments.

The bell

The bell is the smaller, concave cup on the opposite side. It does not have a membrane covering it. Instead, the patient's skin itself acts as the vibrating surface when you press the open bell against it.

The bell excels at picking up low-frequency sounds, such as certain heart murmurs (particularly mitral stenosis), bruits, and the third and fourth heart sounds (S3 and S4). It is also preferred for auscultating smaller patients, including children and thin adults, where a large diaphragm would not sit flat.

When to use each

Feature	Diaphragm	Bell
Frequency range	High-frequency	Low-frequency
Best for	Breath sounds, bowel sounds, normal heart sounds	Heart murmurs, bruits, S3/S4
Pressure	Firm contact	Light contact
Size	Larger diameter	Smaller diameter
Surface	Flat membrane	Open cup (skin acts as membrane)

Chestpiece construction: stainless steel vs aluminium

The material the chestpiece is made from directly affects both sound quality and durability. There are two main options:

Stainless steel chestpieces (used on the Littmann Cardiology IV, Master Cardiology, and other premium models) are denser and heavier. That extra mass means the chestpiece sits more firmly against the patient's skin, creating a better acoustic seal. Stainless steel also transmits sound vibrations more efficiently, which is why Cardiology-grade stethoscopes consistently outscore lighter models in acoustic tests.

Aluminium chestpieces are lighter, making the stethoscope more comfortable to wear around the neck during a long shift. However, aluminium is softer and less acoustically responsive. Many budget stethoscopes and some mid-range models use aluminium or zinc alloy chestpieces.

The Littmann Classic III uses a machined stainless steel and aluminium combination: the adult side is stainless steel for sound quality, while the smaller paediatric side is lighter aluminium. This keeps the overall weight manageable without sacrificing acoustic performance on the side you use most.

What makes Littmann stethoscope parts different?

Several Littmann-specific engineering features set their stethoscopes apart from standard models.

Tunable diaphragm technology

This is the single biggest innovation in modern stethoscope design. With a traditional stethoscope, you physically flip the chestpiece to switch between bell and diaphragm. With Littmann's tunable diaphragm, you switch between low and high-frequency sounds simply by changing how much pressure you apply.

Light pressure on the diaphragm side lets low-frequency sounds through (mimicking a bell). Firm pressure filters those out and emphasises higher-frequency sounds. This means you can hear both frequency ranges without repositioning the chestpiece, saving time and reducing disruption for the patient.

On the Littmann Classic III, both the adult and paediatric sides feature tunable diaphragms. The paediatric side can also be converted into a traditional open bell by swapping the diaphragm for the included non-chill rim.

Dual-lumen tubing (Cardiology IV)

As mentioned above, the Cardiology IV houses two completely separate sound channels inside a single tube. This delivers cleaner acoustics without the bulk or noise of two separate tubes. It is one of the key reasons the Cardiology IV scores 9 out of 10 on Littmann's own acoustic performance scale, compared to 7 out of 10 for the Classic III.

For a detailed side-by-side breakdown, see our Littmann Classic III vs Cardiology IV comparison.

Quick-reference: stethoscope parts and their functions

Part	What it does	Littmann advantage
Ear tips	Seal ear canals to block ambient noise	Soft-sealing design for comfort and noise reduction
Ear tubes	Connect ear tips to tubing at the correct angle	Anatomically angled headset for optimal fit
Tubing	Carries sound from chestpiece to ears	Next Gen material (latex-free, resists oils/alcohol); dual-lumen on Cardiology IV
Stem	Connects chestpiece to tubing; switches active side	Recessed spline with visual indicator
Diaphragm	Detects high-frequency sounds (breath, heart)	Tunable: light pressure = low freq, firm = high freq
Chestpiece	Houses diaphragm and bell; contacts the patient	Machined stainless steel (Cardiology IV) for superior acoustics
Bell	Detects low-frequency sounds (murmurs, S3/S4)	Convertible: swap diaphragm for open bell on Classic III

Which Littmann is right for you?

If you are a nursing or medical student, a GP, or a nurse looking for a reliable all-rounder, the Littmann Classic III covers everything you need. Its dual tunable diaphragms, convertible paediatric side, and 5-year warranty make it the go-to choice for general clinical work.

If you are a doctor, paramedic, or specialist who needs the highest acoustic performance for cardiac assessments, the Littmann Cardiology IV is the step up. The dual-lumen tubing, stainless steel chestpiece, and 9/10 acoustic rating deliver noticeably sharper sound, particularly for faint murmurs and low-frequency heart sounds.

Not sure which to pick? Our Classic III vs Cardiology IV comparison guide breaks down the differences in detail.

Frequently asked questions

What are the main parts of a stethoscope?

A standard stethoscope has six main parts: the ear tips (earpieces), ear tubes (binaural), tubing, stem, and a chestpiece containing a diaphragm and bell. Each part works together to transmit body sounds from the patient to the clinician's ears.

What is the difference between a stethoscope bell and diaphragm?

The diaphragm is the larger, flat side that picks up high-frequency sounds such as breath sounds and normal heart tones. The bell is the smaller, concave side that picks up low-frequency sounds such as heart murmurs and S3/S4 heart sounds. You use firm pressure for the diaphragm and light pressure for the bell.

What is a tunable diaphragm on a Littmann stethoscope?

A tunable diaphragm lets you hear both high and low-frequency sounds from the same side of the chestpiece by simply changing how hard you press. Light pressure captures low frequencies (like a bell), while firm pressure captures high frequencies (like a traditional diaphragm). This saves time because you do not need to flip the chestpiece.

What is dual-lumen tubing?

Dual-lumen tubing contains two separate sound channels inside a single outer tube. Each ear gets its own dedicated channel, which improves acoustic clarity without the rubbing noise that traditional two-tube designs produce. The Littmann Cardiology IV uses this design.

How often should I replace my stethoscope ear tips?

Replace ear tips when they become hardened, cracked, or no longer seal properly in your ears. For most clinicians using their stethoscope daily, this means every 6 to 12 months. Clean them with an alcohol wipe after each use to extend their life.

Does the length of stethoscope tubing affect sound quality?

Yes. Shorter tubing (around 25 to 27 inches) generally transmits sound better because the sound wave has less distance to travel and less energy is lost. However, the difference with modern high-quality tubing is small, and the standard 27-inch length on most Littmann models balances acoustic performance with practical reach.

What does the chestpiece of a stethoscope do?

The chestpiece is the round metal component placed against the patient's body. It captures sound vibrations and directs them into the tubing. Most clinical stethoscopes have a dual-sided chestpiece with a diaphragm on one side and a bell on the other, letting you switch between high-frequency and low-frequency sounds by flipping it over.

Does chestpiece material matter?

Yes. Stainless steel chestpieces are denser and transmit sound more effectively than aluminium ones. This is why higher-end stethoscopes like the Littmann Cardiology IV use a full stainless steel chestpiece, while more affordable models may use aluminium or a combination of both materials.

Why does my stethoscope sound muffled or quiet?

The most common causes are worn or cracked ear tips that no longer seal in your ears, a crack or split in the tubing, or the chestpiece being on the wrong side (bell instead of diaphragm, or vice versa). Check the ear tips first, as they are the cheapest and easiest fix. If the tubing has hardened or developed cracks, replacing the tubing or the entire stethoscope is usually necessary.

Can you replace individual parts of a stethoscope?

Yes. Ear tips, ear tubes, tubing, and diaphragm membranes are all replaceable on most stethoscope brands, including Littmann. Replacement kits are available from the manufacturer or from medical suppliers like Vena Cava. Replacing worn parts is significantly cheaper than buying a new stethoscope and can restore acoustic performance.

How do I clean and maintain my stethoscope?

Wipe the chestpiece, tubing, and ear tips with a 70% isopropyl alcohol swab after each patient contact. Do not submerge the stethoscope in liquid or use hand sanitiser gels, as these can degrade the tubing over time. Store it flat or hanging rather than folded around your neck, as folding causes tubing to crack at the bend points.

What is the difference between single-sided and dual-sided stethoscopes?

A single-sided stethoscope has only a diaphragm on its chestpiece, while a dual-sided model has both a diaphragm and a bell (or two tunable diaphragms). Dual-sided models are the clinical standard because having access to both frequency ranges is essential for thorough auscultation. The Littmann Classic III is a dual-sided stethoscope where both sides feature tunable diaphragms, effectively giving you bell and diaphragm function on each side without needing to flip.

What stethoscope parts do nurses and paramedics need to know about?

Nurses and paramedics should understand the chestpiece (diaphragm for lung sounds and blood pressure, bell for heart murmurs), the ear tips (proper fit ensures acoustic seal), and tubing (shorter is acoustically better, but 27 inches is the practical standard). For pre-hospital environments, a robust chestpiece and non-chill ring are particularly important since patients are often assessed in cold or noisy conditions.

For a broader comparison of every model, see our Best Stethoscope UK 2026 buying guide.