The Parts of a Stethoscope
Doctors, nurses, emergency responders, veterinarians and a host of other medical professionals use stethoscopes every day.
They are part of every toy doctor’s kit ever sold; heck, even Barbie and Ken have stethoscopes!
You may use your stethoscope so often that you feel as if it has become a part of you, but do you really know how it works?
Have you ever really thought about the parts of a stethoscope?
How they are made and how they all function together to give you the information you need about a patient?
When you know more about stethoscopes you can make better decisions about purchasing them, caring for them and using them.
“Stethos” means “chest,” so this is the logical place to start. The chestpiece is the part of the instrument that you hold against the body of the patient.
It may be single-sided or double-sided.
– A two-sided chestpiece will typically have a diaphragm on one side and a deep cup-shaped side called the bell.
– Both single-sided and double-sided pieces will usually have a flexible ring called a chill ring encircling them, which helps to make an airtight seal and buffer the patient against the coldness of the part.
- The stem is what connects the chestpiece to the tubing.
- Acoustic tubes: The acoustic tubes are the hollow rubber-like tubes that connect the chestpiece to the ear tubes.
- Headset: This is typically the metal portion of the stethoscope.
- Ear tubes: The ear tubes are hollow metal tubes that connect to the acoustic tubes on one end and the earpieces on the other.
- Earpieces: Earpieces are the small tips on the ends of the ear tubes that fit into your ears. Some stethoscopes may have a choice of hard plastic or soft silicone earpieces.
How do Stethoscopes Work?
A stethoscope is a medical device designed to pick up body sounds through vibrations and transmit them to our ears. They are usually composed of a flat or curved chest piece covered highly by a film, like a drum, called the diaphragm. As sound vibrations reach the diaphragm, this vibrates and amplifies these sounds, transmitting them through the sealed hollow tubing into the earpieces and into the user’s ears.
Where stethoscope quality variation comes most into play is how well the stethoscope can pick up sound and transmit these while maintaining it’s characteristics and without losing important sound detail.
Dual-headed stethoscopes have a larger flat surface (the diaphragm) which is better suited to picking up high-frequency vibrations, and a smaller side (the bell) which collects low-frequency vibrations.
The parts of a stethoscope are labeled below in this detailed image.
What Are the Parts Made of?
You might be wondering how a stethoscope actually comes into being.
Different manufacturersmay make the parts out of slightly different materials, but there are some commonalities in their methods.
The chestpiece and the ear tubes are made of metal.
They are most often made of aluminum or stainless steel, but the chestpiece may also be titanium or zinc, and the ear tubes may be brass.
Aluminum parts are made with a process called die-casting.
This means that molten aluminum is poured into a mold to form the basic shape, then the cooled casting is taken out of the mold and worked by machine into the refined final shape.
Stainless steel is not die-cast, since the steel arrives at the manufacturer already formed into rods.
These rods are shaped on a lathe to cut away the excess metal, leaving the desired final shape.
Brass ear tubes are not solid brass; they have an outer coating of brass electroplated onto a base metal.
Manufacturers of stethoscopes usually machine the tubes then outsource the electroplating.
All the soft parts of a stethoscope were traditionally made of rubber, but with the advent of modern materials they may also be made of plastic, silicone or PVC.
Earpieces are most often made of silicone or hard plastic.
They are molded to a size and shape estimated to fit into the typical ear canal.
It is possible to get custom-fitted earpieces if the ones provided with your stethoscope do not fit or function as you would like.
Acoustic tubes today are made of either neoprene or PVC.
Here’s the kicker…
There are two different methods for forming the tubes, and the method used is reflected in the price.
The less expensive method is to mold or extrude the tubes, which allows the finished tubes to be produced in one step.
A more expensive method is to repeatedly dip the tubes, allowing thin layers of material to build up to the desired ultimate thickness.
How Is a Stethoscope Assembled?
This might surprise you…
Stethoscopes are assembled by hand.
First the ear tubes and acoustic tubes are fastened together.
The machining process leaves the ear tubes with a barb on one end.
The ends of the acoustic tubes are heated gently to soften them, making it possible to easily slip them over the barbs which hold them securely in place.
The earpieces are threaded onto the other end of the ear tubes, the diaphragm is snapped into the chestpiece, and the chill ring is stretched around the chestpiece.
All that is left is to attach the acoustic tube to the chestpiece and you have a finished stethoscope.
Want to know the best part…
You will be glad to know there is one more step before the stethoscope goes out the door. Testing and inspection.
Every instrument is visually inspected for flaws that can be seen with the naked eye.
They are also tested with machines that make sure the tubing is airtight, and with devices that stretch the tubing to make sure it is physically durable.
Each stethoscope is also tested for the all-important acoustic fidelity.
There are several levels of quality for stethoscopes, and this is reflected in the way they are packaged.
The least-expensive offerings are often simply dropped into a plastic bag, while the high-end models will be packed in firm material, with recesses allowing the instrument to rest securely, surrounded by a sturdy box.
How Does a Stethoscope Work?
“Stethos” means “chest,” and “scope” means “to examine.”
Fair enough, but how, exactly, does a stethoscope allow you to examine a chest, or a lung, or an abdomen?
All of the parts of a stethoscope and their functions are designed with a single design feature in mind.
It is simply sound waves. In other words, transmit sound waves from the patient to your ears.
A body makes sounds as it goes about its business.
You can hear the heart beating and the valves opening and closing.
Healthy lungs sound hollow, while diseased lungs may wheeze or crackle.
The sounds, or absence of sounds, coming from the abdomen can give you vital clues about what is happening in the gut.
This is crazy…
These sounds may be either low-frequency or high-frequency.
High-frequency sounds are strong enough to directly vibrate the diaphragm of the chestpiece of a stethoscope when it is held against the body.
Low-frequency sounds only make it as far as the skin.
The stethoscope is actually picking up the vibrations in the skin, not the original sound waves, when you listen to low-frequency sounds.
It is the function of the bell side of a double-sided stethoscope to transmit this type of vibration.
When you are using a single-sided stethoscope, the low-frequency and high-frequency sounds are detected as a result of the pressure you exert on the chestpiece.
If you press the chestpiece lightly against the skin you will pick up low-frequency sounds, and if you press more firmly you will hear the high-frequency waves.
From the chestpiece, the sound waves travel up the acoustic tubes.
They bounce off the sides of these tubes and are reflected up to the ear tubes and on to the earpieces.
This is the bottom line explanation for why the tubes need to be airtight and the earpieces need to fit snugly.
Every bit of air that escapes along the path from the chestpiece to your ears reduces the quality and quantity of sound that you hear, and less sound means less information.
Even the tiny chill ring around the chestpiece has an important role to play in preserving the fidelity of the sound transmitted through the stethoscope.
Yes, it adds to the patient’s comfort by separating the metal from the patient’s skin, but it also helps form a seal on the skin to keep vibrations from escaping.
Cleaning and Maintenance of Stethoscopes
Your stethoscope is a hardworking tool. It rarely complains, but there are a few things you can do to keep it healthy and happy.
– Inspect your stethoscope occasionally to make sure there is no obvious damage such as punctured tubing or cracked earpieces.
– Wipe the earpieces and chestpiece regularly with 70 percent isopropyl alcohol to clean and disinfect them.
– The tubing may be cleaned with 70 percent isopropyl alcohol or mild soapy water.
– If you wear your stethoscope draped around your neck, always keep it around your collar. The flexible tubing may become stiff if it is continuously exposed to skin.
– Your stethoscope should not be exposed to solvents, oils, extreme heat or extreme cold, as these could cause the materials to degrade.
– Keep the manual that came with your stethoscope and follow any care and maintenance tips it suggests.
If you follow these simple rules, your stethoscope will provide years of low-maintenance faithful service.
The Last Word
Now that you have this information about stethoscopes, you can make educated decisions about buying and caring for them.
Students who only need something to get through one physiology lab do not need to buy a high-end brand and treat it with kid gloves.
On the other hand, professionals who use a stethoscope every day and rely on it for quality patient care should never try to get by with an inexpensive model.
When you rely on your stethoscope, you need to have a quality brand that has been well made and tested for air-tightness and acoustic fidelity.
You should treat it with care and avoid dropping, stretching or puncturing it.
Store it out of the dog’s reach, don’t leave it in the hot car, have a couple of extra earpieces on hand, and clean it often.
A quality stethoscope is an investment; choosing a model that meets your needs and caring for it appropriately makes it a wise investment that will last for years.
Tags: Parts of a stethoscope, parts of a stethoscope and their functions, parts of a stethoscope bell, parts of a stethoscope labeled
Categorised in: Stethoscope Articles, Stethoscope Guides
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