Ultimate Guide to How Stethoscopes Work

By BestRatedDocs    |     Last Updated: 30 April, 2018

The sound is an important diagnostic tool to identify a patient’s health. It is possible to gain a lot more with an ear from the chest of a person that the heart valve is not fully closing, the bowel is obstructed, or what the size of the liver is.

History of Stethoscope

The first stethoscope was invented in the 19th century by French Physician Rene Laennec. With his invention, it was possible to hear body sounds more clearly. But Lannec was actually trying to gain a rather different end – doctor-patient distance.

Laennec’s stethoscope was eventually a hollow tube. There were progressive innovators created with more intricate designs, combining the efforts of Harvard based Doctor David Littmann’s stethoscope, which is almost the same as the one that hangs around the neck of healthcare providers today. Such stethoscope can track sounds as faint as the fetal heart beats like six weeks into a pregnancy. Besides their most common use of detecting heart, breath, it is possible to measure blood pressure, blood sounds and they can also be critical in detecting abnormalities in venous and digestive systems. read more

How Stethoscope Works

The modern stethoscopes are a far away from the hollow tube design. They are lighter and more efficient than the conventional stethoscopes. The stethoscope comprises of the following parts  –

  • Chestpiece
  • Diaphragm
  • Bell
  • Ear tips
  • Headset
  • Stem
  • Tubing

Every part of the stethoscope is linked to each other in order to deliver precise sound from patient to the doctor.

You must be aware that sound is mainly an air pressure disturbance. For example, when you strum the string of a guitar, then the string vibrates. Such vibrations lead to fluctuations in the air pressure as they move outward, traveling in the waves. When such waves cause pressure variations, they reach our eardrums and cause vibration of eardrums. These vibrations are interpreted by the brain.

The eardrum of our body functions like a bigger side of the stethoscope, which is a diaphragm.

When a nurse or doctor places stethoscope diaphragm on the chest of the patient, sound waves travel through the body of patients causing a flat surface of the diaphragm to vibrate. Such vibrations would travel externally if the diaphragm is a stand-alone unit. For this reason, it is attached to a strong stem and to the tubing so that sound waves are channeled and travel in a single direction.

Eave sound wave reflects or bounces to the inside walls of the rubber tube. This process is known as multiple reflections. This way, each wave in succession reaches to ear tips, then to rubber nubs and to end of the device, and eventually to eardrums of the listener.

The high-frequency sounds, such as heartbeats and breath travel at higher frequencies. This implies that they can result in higher numbers of pressure fluctuations in a specific time period. The high-frequency sounds will directly vibrate the overall surface area of the flat and big disc. This means that the sound waves resulted from closing and opening of an artery, for example, are the ones that travel through stethoscope’s tubing to ears of the doctor.

However, the functionality of bell is quite different. It does not pick the vibrations resulted from the artery movement directly. Rather it picks vibrations in the skin caused by a specific movement. Bell is the hollow, small bell that holds a lesser surface area. It is metal, a thin rim that tracks lower-pitch sounds that may be difficult to vibrate the bigger diaphragm. However, these small frequencies vibrate the skin. Such skin vibrations are tracked by the bell.

The vibrations hit the Chestpiece into a narrow tube. It ensures that the sound travels straight to the eardrums without traveling outward. Hence, this results in amplification of sound and their movement in the eardrum.

An Important Tip!

A vital trick for professionals using a stethoscope is that they must ask the patient to be at least 2feet away from their position. This allows them to hear clearer and louder sounds of the heart, lungs, and bowel movements. If the person’s chest has direct or close contact, then this would make the sounds slightly unclear and interrupted.

Wrapping Up

This is the detailed description of how a stethoscope works. Since a stethoscope is prepared of different parts, so it may not be able to deliver accurate results if anyone of the part is damaged. Hence, when you buy a stethoscope, make sure you check the material and performance quality of every part in order to avail the best results and adequate functionality. Also, there are many types of stethoscopes to cater different medical fields, each designed for a specific purpose. Hence it is important to select the one which caters your functionality.

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