STETHOSCOPES 101

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Dual Head (Combination) Stethoscopes - Consists of a bell and a diaphragm. With the double sided stethoscope, the user should open (or index) the bell or diaphragm by rotating the chest piece. When the diaphragm is open, the bell will be closed, preventing sound from coming in through the bell and vice-versa. Other (not top of the line) dual head stethoscopes have a bell side that is smaller than the diaphragm side that is used for smaller patients and pediatrics. 

 

Single Sided Stethoscopes - Inherently has better sound quality than a dual sided stethoscope, (as long as both stethoscopes are of equal quality).  This is due to the fact there are no moving parts on a single sided stethoscope unlike the dual sided stethoscope which you can rotate to different sides.  Moving parts are used in the rotation process from one head to another of a dual sided stethoscope. 

 

The Bell - The bell side of stethoscope was created to hear low frequency sounds better (example: heart sounds).  A Cardiologist would only use a top of the line stethoscope like the GRx Medical cardiology stethoscopes.  The GRx Medical CD-29 has a diaphragm on the small side that can be converted to a deep cone bell if needed.  99% of all users (including most Cardiologists) don’t convert the small diaphragm to a deep cone bell because the low frequency sound difference between a diaphragm and bell is almost undetectable to most.

 

The Diaphragm - When indexed (opened), the diaphragm allows the user to listen to high frequency sound (i.e. lung sounds).  Tunable Diaphragm Stethoscopes - some manufacturers state that they are the only ones with a tunable diaphragm. All diagrams are tunable depending on the pressure that is exerted. A tunable diaphragm allows the user to hear high and low frequency sound.  For low-frequency sounds, rest the chestpiece lightly on the patient. ... For high-frequency sounds, use firm contact pressure on the chestpiece. Usually light pressure is best for heart sounds and firm pressure is better for Lung sounds.

 

The Chest Piece - The chest piece contributes to the sound quality of a stethoscope. The quality and type of material used to make the chest piece will contribute to the sound quality.  Stainless steel is the most popular material used in high end stethoscopes.  Middle of the line stethoscopes use aluminum or a Zinc Alloy material.

 

The Head Set - The proper headset alignment and the fit of the ear tips are very important for sound quality. Most head sets are at a 15 degree angle.  The angle should be facing forward on the head so as to fit into the ear anatomically correct.  The head set should fit snug in the ears.

 

Ear Tips - There are three types of ear tips: Soft, Semi-Soft and Hard.  Most people prefer the soft or semi-soft.  The degree of softness depends on the manufacturer.  Sometimes, ear tips that are too soft can collapse and restrict sound. Proper fitting ear tips are necessary to achieve optimal acoustic performance. 

 

Factors that can contribute to Poor Acoustics - Inspect your stethoscope regularly. Normal wear and tear, like keeping it in your pocket, may cause obstructions. Stethoscopes rely on airtight seals to transmit sound. Loose parts or cracked tubing can prevent this seal.  There are also differences in hearing (some people have better hearing than others) from one individual to another.

 

The Tubing - The two most popular tube designs: dual and single lumen designs.

The dual tube design consists of two internal tubes, one tube each going to a separate ear. The single lumen design allows sound to be carried to both ears through a single tube. The higher quality stethoscopes have a dual tube design.  The exception to this rule is the Sprague stethoscope which has two external tubes.  The Sprague is old technology, and even thought it does have dual tubing this type of stethoscope is often not as good as a single lumen tube stethoscope.