The Ultimate Guide to Types of Stethoscopes
This combination of metal pieces and rubber tubing is far more than the sum of its parts: The stethoscope is one of the most common diagnostic tools for any medical professional. But shopping for this seemingly simple device quickly becomes complicated as you realize how many options are out there. Should you choose a single head or dual head model? Do you need a specialty version for cardiology or pediatrics? What are your options if you’re hearing impaired?
If you’re in the market for a new stethoscope, we’ve got the answers for you–whether you’re buying your first one for medical school or looking to upgrade your trusty old model. In this guide, we cover the basic anatomy of a stethoscope and break down three types of stethoscope heads. Then, we discuss the many types of stethoscopes, including the various specialty versions and the differences between acoustic and electronic models. And of course, no ultimate guide would be complete without a short history lesson on the invention of the stethoscope!
History of Stethoscopes
It wouldn’t be an ultimate guide if we didn’t talk at least a little bit about the history of the stethoscope. Doctors have been listening to patients’ bodies for diagnoses probably since the practice of healing began, but the concept of the stethoscope didn’t emerge until 1816. French physician Rene Laennec needed to listen to a patient’s chest, so he rolled a long piece of paper into a tube—and realized how much better he could hear using the device than by placing his ear directly against the patient’s body. Laennec coined the term "stethoscope," the Greek words stethos (chest) and skopein (to view or see).
Twenty-five years after Laennec invented the stethoscope, George P. Camman of New York developed a design that featured an earpiece for each ear. Medical professionals continued using this design with few changes for almost a century. It wasn't until the early 1960s that Dr. David Littmann patented a new design that significantly improved the acoustical performance of the stethoscope. 3M acquired Dr. Littmann's stethoscope business a few years later, and the doctor continued to work on his designs. Dr. Littmann’s designs ultimately became the new standard for stethoscopes, and now Littmann is the most trusted brand name in the business.
How Does a Stethoscope Work?
A stethoscope captures sound waves produced within the body. When the chest piece, comprising a bell and a diaphragm, is placed on the patient’s body, it captures low and high-frequency sounds. These sounds cause vibrations in the bell or diaphragm, which are then transmitted through the tubing to the earpieces. The earpieces convert the vibrations back into audible sounds, allowing healthcare professionals to listen attentively to the internal sounds of the body.
By analyzing these amplified sounds, medical practitioners can gather crucial diagnostic information for accurate assessments and improved patient care. In essence, a stethoscope acts as a transducer, transforming acoustic energy into mechanical vibrations and then into audible sounds for medical professionals to interpret..
Parts of a Stethoscope
No matter what type of stethoscope you want to buy, specialty or not, all stethoscopes have the same basic designs and parts. Here are the main components to pay attention to as you shop for stethoscopes.
These tips sit on the ends of a curved metal tube that attaches to the rubber tubing. The ear tips should fit comfortably in your ear and achieve a good seal so you can clearly hear the sounds of the body as you auscultate. Some stethoscope models offer interchangeable ear tips so you can find the right size and fit.
The tube has two important jobs–transmitting sounds from the body while simultaneously dampening or eliminating background noise that might interfere with diagnosis. Look for a tube made from thick, flexible, crack-resistant material that will stand up to a lot of bending.
The chest piece (or head) of most stethoscopes is made from stainless steel, which is very durable and conducts sound well. Some chest pieces are also made from a combination of stainless steel and a zinc or aluminum alloy. The common dual head stethoscope chest piece will feature a diaphragm on one side and a bell on the other (more on the diaphragm and bell in the next section).
The diaphragm is a thin, circular piece of flexible material (often resin) that fits one side of the metal stethoscope head. The diaphragm helps amplify sound, and it should be well-sealed, preferably with a no-chill rim, for optimal results.
Even traditional acoustic stethoscopes offer several options when it comes to the head design. The three main models you can choose from are:
Single head stethoscopes offer only one flat, circular surface for general purpose use, like listening to vital signs, the lungs or the heart. Single head stethoscopes can cover a wide frequency of sounds and allow the user to focus on either the higher or lower end of the spectrum.
Dual head stethoscopes offer two heads, one on each side of the chest piece. The larger one–the diaphragm–is flatter and works better for high frequency sounds. The smaller one–the bell–looks more like an elongated cup and works best on low frequency sounds. Some physicians who see patients of all ages like a dual head stethoscope because the diaphragm side works well for adult patients, while the bell side is more appropriate for smaller pediatric patients.
The most uncommon of the three stethoscope head options, the triple head stethoscope features three heads attached to a single chest piece. As you can imagine, this design is rather heavy and awkward to use, which is why it’s only used for critical cardiac assessment. Most doctors, nurses and other medical professionals use a standard single or double head model.
Specific Stethoscope Uses
Some stethoscopes are tailored to certain types of patients or have designs that are intended to enhance certain functionalities. Your options are:
As the name implies, cardiology stethoscopes are used in cardiac assessments to distinguish between the many different sounds of the heart for the most precise diagnosis. Both single head and double head chest pieces are available. (To learn more about what sets a cardiology stethoscope apart, check out our review of the 3M Littmann Cardiology IV Stethoscope.)
Small patients need equally small medical instruments. A pediatric stethoscope looks just like a regular stethoscope, except that the head is scaled down until it’s about an inch in diameter so it will be more proportional to pediatric patients. There are also infant stethoscopes available, which feature even smaller chest pieces for the very tiniest of patients.
For medical professionals who treat mammals other than humans, they might want to consider a veterinary stethoscope, which is specially designed to be used on popular pets such as dogs and cats. Some veterinarians also turn to pediatric and/or infant stethoscopes to treat smaller pets, such as lizards and birds.
This distinct design of stethoscope features two tubes that reach directly from the stethoscope chest piece to the metal curved ear piece. The tubes are held together with metal clips so they don’t separate. The double-barreled design is intended to boost sound quality.
Even the heaviest specialty stethoscope usually tops out around 175-185 grams (0.4 pounds), but even the slightest weight around your neck can be terrible if you already have neck or back pain—especially if it’s a stethoscope you have to wear all day. For these medical professionals, stethoscope gold standard Littmann makes a couple Lightweight and Select models that weigh more in the range of 115-120 grams. Keep in mind that these lighter weight stethoscopes may not offer the same high level of sound precision as other models, as additional features or better construction often translate to more weight.
Types of Stethoscopes
Technology has changed even the way the good old stethoscope works. Below, we explain the workings of a traditional acoustic stethoscope before comparing it to two other types of stethoscopes: electronic and hearing impaired.
An acoustic stethoscope works by channeling more sound waves toward your ears than would otherwise reach them. In order for us to hear a noise, sound waves must cause vibrations in air molecules, causing changes in air pressure that make our eardrums vibrate in turn. Bodily sounds like a heart beating or a stomach gurgling cause sound waves, which hit the metal chest piece of the stethoscope when you place it on a patient.
The rubber tube then channels these sound waves in a specific direction until they hit the metal earpiece and then finally your ears. Because the sound waves are contained by the tubing, more of them reach your ears than would otherwise, amplifying the sound. This is why listening to a patient’s heart on a stethoscope sounds louder than putting your ear right next to their chest.
As amazing as acoustic stethoscopes are, they are limited in how much they can amplify sounds. Electronic stethoscopes (also called digital stethoscopes) take the physical vibrations of the sound, translate them into an electronic signal and optimize them for improved listening and diagnosis. Some electronic stethoscopes also have the ability to reduce background noise in addition to simply increasing the volume.
Certain digital stethoscopes may offer additional features. For example, the Littmann Electronic Ambient Noise Reduction 3200 model can store twelve 30-second tracks onboard the stethoscope, along with a 10-second comment to notate the sound. Littmann stethoscopes also offer an LCD display that includes frequency selection, sound level, remaining battery life and patient's heart rate. Other models connect to apps that visualize the audio data. The stethoscopes may transmit the data to the apps via Bluetooth or a plug-in cord.
Most electronic stethoscope models are designed like a regular stethoscope, but a couple of them—such as the Thinklabs One Digital Stethoscope—are simply a chest piece that plugs directly into a pair of headphones. Electronic stethoscopes are either battery-powered or rechargeable, so if the battery is dead or you’ve forgotten to charge it, it won’t work. However, the substantial sound amplification (up to 24x for Littmann electronic models) is worth the trade-off for many users.
Stethoscopes for Hearing Impaired
For medical professionals who have hearing loss, there are several options available. An amplified electronic stethoscope, as described in the section right above, will increase the volume of the sounds to make them more audible. If you don’t wear hearing aids, you can use this stethoscope like normal. If you do wear hearing aids, you can try out special adaptors called stethomate tips, which allow you to use the stethoscope with your hearing aids.
If wearing a traditional stethoscope with your hearing aids is uncomfortable, another option is to use a digital stethoscope that you can plug headphones into. As long as you choose a large enough pair of headphones (look at over-ear and on-ear models), they should fit over your hearing aids just fine. Depending on the brand of both your hearing aids and digital stethoscope, you might be able to purchase a transmitter that will wirelessly transmit the sounds from the stethoscope to the hearing aids.
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