Stethoscope Bell Vs Diaphragm, A Comprehensive Comparison

May 24, 2018

Stethoscope Bell Vs Diaphragm, A Comprehensive Comparison

Understanding acoustic stethoscopes

Before we get into Stethoscope Bell vs Diaphragm, let's look at 2 main types of stethoscopes. When it comes to stethoscopes, there are many different ways of classifying. You can have types based on intended application, appropriate age group to use on or even mechanism of sound reception and transmission. With the last example, there are two main types of stethoscopes; acoustic and electronic. With electronic stethoscopes, all the information is gathered and compiled on the chest piece using special sensors and transducers. The main advantage they offer is the fact that there is little interference or loss of clarity during transmission. They also facilitate automation of things like calculating heart and breathing rates. Acoustic stethoscopes on the other hand basically rely on good old-fashioned vibration and sound transmission through the reflection of the waves. Sensitive membranes on the chest piece receive and mimic vibrations from the skin and deeper tissues. These vibrations are transmitted as waves through tubing designed to allow continuous reflection until the sound reaches the ears through the headset. This traditional design is simple but highly effective. It ensures high quality and high clarity sound transmission with very absolutely no alteration of the original sound waves. Acoustic stethoscopes always feature some version of the bell and diaphragm. Below is a comprehensive comparison of the stethoscope bell vs diaphragm to help you understand how they work.

Stethoscope Bell Vs Diaphragm

Chest piece design

The bell usually takes the form of a hollow cup or cone. With some models, this is covered by a membrane similar to that on a diaphragm but significantly smaller in diameter. The bell is designed to pick vibrations from the skin which is made easy and accurate with this particular design. With tunable stethoscopes, all you have to do to mimic a bell is release pressure applied to the chest piece. Diaphragms on the other hand feature a plastic or fiberglass membrane stretched over the chest piece's wide base. The diaphragm membranes are made from material very sensitive to fine vibrations from deep tissues including lungs, airways and heart valves. With tunable stethoscopes, you can achieve the same results by simply increasing pressure applied to the chest piece.

Sensitivity

The bell is highly sensitive to low-frequency sounds. These are easily picked on the skin surface of the person being examined. The Diaphragm is sensitive to both low and high-frequency sounds. However, it is designed to filter out low-frequency sounds making it more sensitive to high-frequency sounds. The high-frequency sounds are amplified as the waves vibrate against the stiff membrane. This allows accuracy and clarity in the transmission of sound from the chest piece to the tubing and finally into your ears.

Sound quality

Bell - The sound quality relies heavily on the stethoscope design and features. However, the bell side usually has more muffled sound. This means that you need to be a bit more attentive as you listen for heart sounds to ensure that you get accurate results from your examinations. Diaphragm - Due to the nature and design of diaphragm stethoscopes, sound transmitted is usually very sharp and clear. This makes it easy to identify and distinguish different sounds during the examination process.

Applicability

Bell - Application depends on the sensitivity of the stethoscope chest piece. With bell stethoscopes, you will be listening for things like the 3rd and 4th heart sounds (S3 and S4 sounds) in the diastolic phase. These are important when examining for conditions including congestive heart failure, dilation cardiomyopathies, and valvular regurgitation. The diaphragm, on the other hand, is used to listen to high frequency sounds including, wheezing and lung crackles in the respiratory system and intestinal noises during abdominal auscultation. When it comes to examining the heart, the diaphragm comes in handy when listening for first and second heart sounds (S1 and S2). These are relevant in conditions like valvular stenosis, aortic insufficiency, fistulas and many other heart anomalies that affect the systolic phase.

Final verdict- which is better?

After all, is said and done, none is better than the other. It truly all depends on what you need from your instrument. The good news is that you do not really have to choose between these two acoustic stethoscope designs. These days, you can get a dual-sided chest piece or one with a tunable diaphragm. These designs allow you to easily switch between sensitivity to high frequency and sensitivity to low-frequency sounds on the same stethoscope for the best of both worlds. Hope you found this article on Stethoscope Bell vs Diaphragm useful.

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