All About Stethoscopes: History, Parts, Types, Reviews, Price.

Stethoscopes: Introduction

The stethoscope is a very important medical diagnostic tool. It is probably the simplest and most useful diagnostic tool available to a medical practitioner. No other medical accessory symbolizes a healthcare practitioner more than a stethoscope (not even a white coat).

The mastery of a stethoscope is very valuable for a healthcare practitioner and it is a very rewarding skill for any healthcare practitioner to have. Stethoscopes are mainly used by healthcare professionals to pick up cardiac (heart) and pulmonary (lungs and breathing) sounds for easy listening.

It is straightforward to use a stethoscope. However, interpreting the internal organ heard through a stethoscope requires skill, experience, and diligence. The first step towards being a pro at stethoscope use is to understand how a stethoscope works and then choose the right stethoscope.

Therefore, this article provides you with detailed information on how a stethoscope works, its history, its parts, the different types of stethoscopes, and how to use and choose a stethoscope.

The stethoscope has a very modest origin. The first-ever stethoscope was just a paper tube. Nowadays, there are sophisticated electronic stethoscopes that use digital technology and artificial intelligence to make diagnostic calls without a doctor’s or nurse’s human judgment. However, the working principle is the same for all stethoscopes from the paper tube to the electronic stethoscope and everything in between.

Below is the outline for this article:

• • history of the stethoscope
  • who invented the stethoscope
  • the parts of a stethoscope
  • how to wear and use a stethoscope
  • how a stethoscope works
  • types of stethoscopes

(including digital stethoscopes)

• Top stethoscope brands (e.g. 3M Littman, MDF, ADC, Welch Allyn EKO, ThinkLabs)

• • what you can do with a stethoscope
  • how to pick a good stethoscope
  • where to buy a stethoscope
  • how to care for a stethoscope (with a brief discussion on disposable stethoscope)
  • Veterinary stethoscope

(stethoscope for pets)

• Conclusion on stethoscope​

History of the Stethoscope. Who Invented the Stethoscope?

The original stethoscope was invented in 1816 by the French physician René Theophile Hyacinthe Laënnec (1781–1826).

Before the invention of the stethoscope by Laënnec, auscultation (the act of listening to the sounds of internal organs for regular and irregular beats) was done by placing the ear on the body of the patient.

However, Laënnec thought this was an awkward practice. Hence, he came up with the idea of the stethoscope for a less invasive means of listening to the sounds of internal organs such as the heart, the bowels, the lungs, etc.

Aside from the awkwardness factor, ear-over-body auscultation was also unhygienic especially when physicians are dealing with patients with highly communicable diseases.

Besides, the ear-over-body technique was prone to errors because there is a limit on how reliable unaided ears could pick up the very weak sounds of internal organs like the heart, arteries, and lungs.

Laennec made his first stethoscope by rolling a paper into a hollow cylindrical tube. He placed one end of the tube on the patient’s chest and placed his ears on the other end of the tube.

Laënnec was surprised and delighted when he was able to hear the patient’s organ clearly through the tube. Laënnec later changed the material of his tube stethoscope from paper to wood and brass.
During his brief lifetime, Laënnec used his invention to identify and classify many chest diseases. He also introduced the medical world to new clinical words that are still in use today.
Words such as ‘auscultation’ and ‘stethoscope’ originated from Laënnec. Ironically, Laënnec died of chest disease, tuberculosis, at the age of 45.

Laënnec stethoscope invention was later revised by others. The most remarkable revision of his invention was the binaural stethoscope, which unlike the original stethoscope, could be attached to both ears.

The binaural stethoscope bears more resemblance to the modern stethoscope than Laënnec’s original invention. However, the principle of operation of early and later stethoscopes are the same.

The binaural stethoscope was invented by Irish the Irish doctor Arthur Leared in 1851, and later perfected for commercialization by American doctor George P. Cammann in 1852.

The next major revision to the stethoscope was made by Harvard Professor and Cardiologist, David Littmann.

In the 1960s, Littman’s invented a commercial binaural stethoscope that had better acoustic performance than earlier stethoscopes. Also, Littmann’s new stethoscopes were lighter in weight.

Littmann’s business line of stethoscopes was later acquired by the American Multinational Conglomerate, 3M. 3M branded Dr. Littmann’s stethoscope as 3M™ Littmann® Stethoscopes.

The next great leap in stethoscope technology was the invention of commercially viable electronic stethoscopes in the 1990s.

Unlike previous mechanical stethoscopes that merely channel sound from the patient’s body to the physician’s ear, electronic stethoscopes amplify the body sounds that are picked up by the stethoscope. This allows medical professionals to hear body sounds with more clarity. Electronic stethoscopes also employ noise reduction/noise cancellation technology for better quality sounds.

Electronic stethoscopes allow medical professionals to hear organ sounds that are difficult to hear with the conventional stethoscopes.

What are the parts of a stethoscope? What materials is a stethoscope made of?

The main parts of a stethoscope are:

• Chestpiece
• Adult diaphragm
• Pediatric diaphragm/bell
• Tubing
• Headset
• Eartips

The stethoscope consists of the chestpiece that goes on the body of the patient. Though called the ‘chestpiece’, the chestpiece can be placed over the lungs, or bowels, and not necessarily on the chest. The chestpiece consists of a large surface adult diaphragm side for auscultating adult patients. It also has a small surface area diaphragm/bell for auscultating pediatric patients with smaller internal organs. The smaller surface area of this part of the stethoscope ensures that health care professionals can place the diaphragm on specific internal organs of interest without picking up noise from other organs.

The Chestpiece

Many modern stethoscopes have chestpieces with tunable diaphragm. This means the same diaphragm can be used to pick up low-frequency and high-frequency organ sounds. In earlier stethoscopes, the large side of the chestpiece, with the large diaphragm, was used to pick up high-frequency sounds of internal organs. The smaller side of the chestpiece small was used to pick up low-frequency sounds of internal organs, sounds like gallops, and rumbles.

The chest piece is made of a metallic material. This metallic material can be stainless steel, titanium, or aluminum. The metallic chest piece is fitted with a non-chill rim to prevent patients from experiencing discomfort should from the coldness of the bare chestpiece.

The material used to make the diaphragm is Epoxy or Fiber Glass.

The Adult Diaphragm

The Adult Diaphragm is the large side of the chestpice and it is used for auscultating adult patients. In a stethoscope with a tunable diaphragm, the diaphragm is tuned by the amount of pressure exerted on when the diaphragm is placed on the body.
Exerting a firm pressure on the diaphragm allows the diaphragm to pick up high-frequency organ sounds while exerting a light pressure allows the stethoscope to pick up low-frequency organ sounds.

The Pediatric Diaphragm/Bell

As mentioned earlier, the pediatric diaphragm part of the chestpiece is used to pinpoint the sounds of the internal organs of smaller patients. The small area of this diaphragm ensures that the diaphragm does not pick up noise from the sound of other organs that are not of auscultation interest to the doctor or nurse performing the auscultation.

The pediatric diaphragm of the on some stethoscope can be removed. Doing this turns this side of the stethoscope into what is called a ‘Bell’ that can be used to pick low-frequency organ sounds. When the stethoscope is used like this, the skin of the patient acts like the diaphragm.

However, some modern stethoscopes still maintain a separate true bell and a separate true diagram on the chest piece, instead of a tunable diaphragm.

The Tubing

The tubing channels the organ sounds of the patient from the chestpiece to the ear of the doctor or nurse examiner. The tubing is made of a thick material to block surrounding noise from reaching into the tube and corrupting the organ sound that is being transmitted in the tube.

The stethoscope tubing is made of a synthetic plastic called Polyvinyl chloride (PVC). The plastic is synthesized with chemicals that do not contain latex to accommodate patients with latex allergies.

The stethoscope tubing comes in different colors. A doctor or nurse can pick a tubing color that suits his or her style. The color of the tubing does not affect the performance of a stethoscope.

The Headset

The headset consists of the aural tubes and the eartips of the stethoscope. The aural tubes extend the tubing into the tubes that go into the ears of the doctor or nurse examiner. At the ends of the headset are the eartips of the stethoscope. The eartips of the stethoscope go into the ear canal of the doctor or nurse.

Stethoscope designed for lightweight have headsets made with aircraft-grade aluminum alloy. Stethoscopes designed for ruggedness have headsets made with stainless steel.

The Eartips

The eartips channels the sound from the aural tubes into the ear of the doctor or the nurse. It also provides an acoustic seal that prevents external noise of the environment from reaching the ear of the doctor or nurse.

The eartips, which go inside the doctor’s or nurse’s ear canals, are made of silicone, a biocompatible material.

The eartips on stethoscopes are usually removable. This allows the user of the stethoscope to pick and use the eartips that he or she found most comfortable for his or her ears.

How to properly wear and use a stethoscope

To properly wear and use a stethoscope:

• Place the stethoscope in front of your face
• Put the two earptips of the stethoscope in contact with each other
• Make sure the eartips point out in the same direction as your nose
• Then put the eartips in your ears
• Finally, place the chestpiece over the patient’s body
• Listen carefully for the internal organ sounds of the patient

When worn properly, stethoscopes conform with the anatomy of your ear so that the eartips of the stethoscope go over your ear canals.

How does a stethoscope work?

A Stethoscope channels body sound waves picked up by the stethoscope’s chestpiece to the ears of a healthcare worker. Stethoscopes can be grouped into two classes based on how stethoscopes work:

• Manual Acoustic stethoscopes
• Electronic Stethoscopes/Digital Stethoscopes

Manual Acoustic Stethoscopes

The manual acoustic stethoscope use only the physical vibrations of sound for operation. Sounds are pressure waves: compression and rarefaction of air. Sounds are made by the vibration of air. The internal organs make sounds by physically vibrating or palpitating. When a stethoscope is placed over an organ, the organ sounds are transferred and coupled to the diaphragm of the stethoscope. The diaphragm vibrates in sympathy with the organ sounds. This in turn vibrates the air around the diaphragm. Since the diagram connects to the tubing of the stethoscope via the chest piece, the air in the tubing of the stethoscope will also vibrate. Since the diaphragm has a wider area compared to the cross-sectional area of the stethoscope tubing, slight vibration of the air around the diaphragm results in large vibration of the air in the narrow stethoscope tubing.
Hence, the air vibration (sound) reaching the ear of the health practitioner gets focused on the ears and therefore appears to be ‘amplified’. This effect is similar to the way the hydraulic system works.

Furthermore, the tubing provides acoustic insulation of the organ sound propagating in the tubing. This means the walls of the tubing prevents external environmental noise from reaching inside the tubing and corrupting the organs sounds propagating in the tubing.
Also, the earpieces of the stethoscope seal the ear of the doctor or nurse from picking up noise coming from the outside environment. This provides the doctor or the nurse the ability to distinctly hear the internal organ sound picked up by the stethoscope.
Technically, the manual acoustic stethoscope does not amplify the sound of internal organs, in the strict sense of the word ‘amplify’. Amplification requires an external source of power which an acoustic stethoscope does not have. Rather the acoustic stethoscope focuses organ sound into the ears of doctors, and this allows doctors to hear organ sounds.

Electronic Stethoscope/Digital Stethoscope

Electronic stethoscopes were invented in the 1990s to make the weak auscultation sounds louder and clearer for better diagnosis. Electronic stethoscopes use electronic microphones to pick up auscultation sounds. These sounds are then digitized into an electronic signal by a circuit. The sounds are then amplified, digitally processed, and then transmitted over wires or wireless to the earphone attached to the ears of a healthcare practitioner. Unlike acoustic stethoscopes, electronic stethoscopes are powered by an external power source such as batteries. Electronic stethoscopes amplifier body sound in the true sense of the word ‘amplify’. Some electronic stethoscope also uses noise cancellation technology to reduce ambient noise reaching the ears to the healthcare practitioner.
Electronic stethoscopes also allow the recording of body sounds unto the internal memory of the stethoscope. Also, an electronic stethoscope can stream the digital sounds from the stethoscope over a wireless work to a computer, tablet, or mobile phone for display and recording. These recorded sounds can later be carefully replayed and analyzed by a healthcare practitioner. Furthermore, some electronic stethoscopes have telemedicine capabilities such that the stethoscope can be placed on a patient, and the auscultation signals transmitted over the internet to a health care professional at a remote location. Also, these stethoscopes have sound filters that allow the healthcare practitioner to selectively focus on body sound frequencies of interest. ​

Some electronic stethoscopes also have artificial intelligence capabilities. This means these stethoscopes can analyze auscultation sound signals and diagnose illness automatically with machine learning.
Moreover, some electronic stethoscope manufactures also manufacture adapters that can be fitted to manual stethoscopes to convert such manual stethoscopes to electronic stethoscopes.

The disadvantage of electronic stethoscopes is their higher cost. Also, electronic stethoscopes need to be continuously powered, either by a battery or by a USB hub. Also, electronic stethoscopes, due to the electronic circuitry and signal processing techniques they employ, are prone to introducing sound artifacts into the body sounds that they produce.​

It is not recommended that healthcare practitioners adopt electronic stethoscopes early in their careers because the art and practice of auscultation are best mastered with an acoustic stethoscope.

Types of Stethoscopes and Different Variations of a Stethoscope

The major types of stethoscopes are:

• Clinician Stethoscope
• Cardiology Stethoscope
• Pediatric Stethoscope
• Neonatal/Infant Stethoscope
• Fetus Stethoscope
• Lightweight Stethoscope
• Electronic Stethoscope/ Digital Stethoscope

Clinician Stethoscope

The clinician stethoscope is for general use and diagnosis in regular non-critical care environments such as in a doctor’s office, physician assistant’s office, urgent care clinic, ambulatory clinic, and gynecological clinic. This stethoscope has acoustic performance that is adequate for non-critical use.

Cardiology Stethoscope

The cardiology stethoscope has superior acoustic performance compared to the clinician stethoscope. It can pick up sounds that the clinician stethoscope cannot pick up. Its superior sound performance allows it to be used in mission-critical environments such as in cardiac intensive care units, emergency wards, and step down units.

Pediatric Stethoscope

Pediatric stethoscopes have smaller chest pieces compared to adult stethoscopes. This allows these stethoscopes to be used to auscultate pediatric patients. Also, many regular stethoscope have a smaller chest piece side for pediatric patients, in addition to the large chestpiece side for adults. Furthermore, some stethoscopes have screw-on chest pieces that are removable and replaceable. These larger chest pieces can be replaced by smaller chest pieces, effectively converting these regular stethoscopes to pediatric stethoscopes.
Pediatric stethoscopes are used by pediatric doctors and nurses, neonatologists, and Neonatal Intensive Care Unit (NICU) nurses.

Neonatal/Infant Stethoscope

Infant stethoscopes have even tinier chestpieces compared to pediatric stethoscopes. Infant stethoscopes are designed to be used on infants. Infant stethoscopes are used by pediatric doctors and nurses, neonatologists, and Neonatal Intensive Care Unit (NICU) nurses.

Fetus Stethoscope

Fetus Stethoscope also known as Pinard horns are used to monitor fetal heart rate. Fetus stethoscope resembles an ear horn. Fetus stethoscopes are monaural, which means they have one eartip. However, most modern hospitals use ultrasound to measure fetal heart rate instead of using a fetus stethoscope.

LightWeight Stethoscope

Lightweight Stethoscopes are made with lightweight materials such as aluminum instead of steel.

Electronic Stethoscope/ Digital Stethoscope

Electronic stethoscopes use digital technology for auscultation. Electronic stethoscopes were discussed earlier on this page.

Top Stethoscope Brands

The top brands of stethoscopes are:

• 3M’s Littmann Stethoscopes
• American Diagnostic Corporation (ADC) Stethoscopes
• MDF Instruments Stethoscopes
• Omron Stethoscopes
• Welch Allyn Stethoscopes
• Eko Electronic Stethoscopes
• Thinklabs Electronic Stethoscopes

3M’s Littmann Stethoscopes

3M’s Littmann Stethoscope brand is the most recognized stethoscope brand in the world. 3M grades its Littmann’s stethoscopes on a scale of 6 to 10+ in terms of acoustic performance. The higher this number, the better the acoustic performance of the stethoscope. The stethoscope categories under the 3M Littman stethoscope brand are Cardiology stethoscopes, Classic Stethoscopes, Lightweight stethoscopes, and electronic stethoscopes.

The specific stethoscopes under the Littman Cardiology stethoscope category are:

• The Master Cardiology™ Stethoscope
• The Cardiology IV™ Stethoscope

The specific stethoscopes under the Littmann Classic stethoscope category are:

• Master Classic II™ Stethoscope
• Classic III™ Stethoscope
• Classic II Pediatric Stethoscopes
• Classic II Infant Stethoscopes

The specific stethoscope under the Littmann Lightweight stethoscope category is:

• Lightweight II S.E. Stethoscope

The specific stethoscope under the Littmann Electronic stethoscope category is:

Electronic Stethoscope Model 3200

3M Littmann also sells replacement parts for its stethoscopes.

Importantly, 3M Littmann also provides, with the purchase of a 3M Littmann stethoscope, a free educational app for learning about auscultation sounds of the heart and lungs.

American Diagnostic Corporation Stethoscopes

American Diagnostic Corporation (ADC) is a New-York based medical diagnostic company that manufactures stethoscope, among other medical diagnostic tools. ADC’s stethoscope product line includes the

• Electronic Stethoscope: the Adscope 658
• Traditional Cardiology Stethoscope: the Adscope® 602
• Clinician Stethoscope: the Adscope® 603
• Ultra-lite Clinician Stethoscope: the Adscope® Lite 619
• Infant Clinician Stethoscope: the Adscope® 605
• Sprague Stethoscope: Proscope™ 640
• Disposable Stethoscope: Proscope™ 665

MDF Instruments Stethoscopes

MDF Instruments manufacture and sell high-quality handcrafted stethoscopes for healthcare practitioners and veterinarians.

MDF’s stethoscope line includes:

• Cardiology Stethoscopes: MDF® ProCardial Core™ Cardiology Stainless Steel Dual Head Adult-Pediatric Stethoscope
• Epoch Stethoscope: MDF® MD One® Epoch Titanium Stethoscope
• MD One Stethoscope: MDF® MD One® Stainless Steel Dual Head Stethoscope
• Acoustica Stethoscope: MDF® Acoustica® Lightweight Dual Head Stethoscope

Omron Stethoscopes

Omron, the Japanese electronics maker also manufactures stethoscopes. Omron manufactures the Omron Sprague Rappaport Stethoscope.

Welch Allyn Stethoscopes

Welch Allyn is a New-York based manufacturer of stethoscopes. In th Welch Allyn’s stethoscope product line are the:

• Harvey DLX Stethoscope s
• Disposable Uniscopes
• Harvey Elite Stethoscopes
• Lightweight Stethoscopes
• Adult Stethoscopes
• Pediatric Stethoscopes

Eko Electronic Stethoscopes

Eko manufactures and sells digital stethoscopes only. Eko’s CORE Digital Stethoscope its Eko’s main digital stethoscope model. This stethoscope uses an electronic microphone to pick up auscultation body sounds. This stethoscope can amplify body sounds by a factor of 40.

The stethoscope also has adjustable volume control and an inbuilt battery. It can also be charged via a micro USB port. This stethoscope can be connected wirelessly to a mobile device over Bluetooth so that auscultation sound can be streamed from the stethoscope to the mobile device. The digital stethoscope also supports Artificial Intelligence analysis of captured auscultation sounds.

Eko also offers an accessory called the CORE Digital Attachment. This is an adapter that can be attached to manual acoustic stethoscopes (such as Littmann’s Clinician Stethoscope, ADC’s stethoscope, WelchAllyn, MDF, and Medline etc) to convert these manual stethoscopes into digital stethoscopes ( with wireless capability, etc). Eko’s CORE Digital Attachment can be fitted to these manual stethoscopes without the need to cut these stethoscope to attach Eko’s digital attachment.

ThinkLabs Stethoscopes

ThinkLabs was founded in 1991 as an electronic medical company, and it released its first digital stethoscope in 2003. Like Eko, ThinkLabs deals in digital stethoscopes alone. Its Thinklabs OneDigital Stethoscope is very lightweight and boasts an amplification factor of more than 100x (compared to 40x of Eko’s). However, unlike Eko’s stethoscope, this stethoscope cannot stream auscultation sound from the chestpiece to the earpieces. It requires a wired headphone or earphone from the chestpiece to the ears.

Where to buy a Stethoscope

Most stethoscopes are available for sale on online stores like Amazon.com and Walmart.com. Manufacturers of stethoscopes also sell stethoscopes on these manufacturers’ websites. Also, a lot of third-party websites such as Medisave.net offer quality stethoscopes for sale at discounted prices.

How to care for a Stethoscope

Research has shown that 89% of stethoscopes were contaminated with one or more microorganisms. Research has also shown that the bell and diagram of stethoscopes are contaminated with superbugs 32% of the time. This appalling statistics undercuts the hygienic motivation that led to the adoption of the stethoscopes for clinical use.

 

Hence, to make the stethoscope live up to the dreams of its inventors, it is important to maintain good hygienic practices when using a stethoscope. More importantly, good hygienic practice ensures the well-being of the patient and the healthcare practitioner. To take good care of a stethoscope:

 

• Clean your stethoscope with 70% by volume isopropyl alcohol solution for disinfection
• Clean your stethoscope with mild soapy water to remove dirt
• Do not clean your stethoscope with hand-sanitizer because chemicals in the hand sanitizer can damage the stethoscope
• If your stethoscope needs sterilization, use low-temperature gas sterilization to sterilize your stethoscope.

For general maintenance of your stethoscope:

• Do not expose your stethoscope to prolonged sunlight
• Do not expose your stethoscope to extreme heat
• Do not immerse your stethoscope in water

 

If you are extremely particular about maintaining strict hygienic practices with a stethoscope, consider buying a stethoscope with a disposable diaphragm which allows you to replace the diaphragm of your stethoscope with a new uncontaminated diaphragm at any time you want. An example of a stethoscope with a disposable diaphragm MDF Instruments stethoscopes. Dirty/contaminated diaphragm of MDF stethoscopes can be replaced with their MDF’s disposable PureSona Diaphragms.

 

For situations where extreme universal precautions are required when using a stethoscope, consider using a one-patient disposable stethoscope. These are stethoscope type is designed to be used on only one patient and then discarded. An example of such a stethoscope is the Welch Allyn Uniscope.

 

Also, one of the merits of digital stethoscopes with wireless capability is that they are more hygienic. This is because, with an electronic stethoscope, the healthcare practitioner may wear a hazmat suit and still be able to auscultate a contagious patient as long as the healthcare practitioner has on his/her wireless eartips. This is possible because in such electronic stethoscopes, sound transmission between the chestpiece on the patience and the eartips on the health care practitioner is done wirelessly over Bluetooth.

Veterinary stethoscopes (stethoscopes for pets)

There is no difference between stethoscopes for humans and stethoscopes for animals. All the aforementioned stethoscopes can be used on pets. However, because of the small sizes of pets, the pediatric or infant stethoscope may be more suitable for pets than adult stethoscopes.

Conclusions on Stethoscopes

The stethoscope is an iconic medical diagnostic instrument. It is an important tool in the arsenal of doctors, nurses, EMTs, and medical students, veterinarians. For additional information on the stethoscope, watch our video on the stethoscope below.

Do you own a stethoscope or are you thinking of buying one? Tell us about your experience with a stethoscope or your customer journey to buying a stethoscope. Please, comment in the section below.