The Dual Head Stethoscope is a versatile general purpose device. The diaphragm mode is used for high frequency heart sounds while the bell mode is used for lower frequency lung sounds. The user selects the bell or diaphragm by rotating the chest piece.
This is the most popular stethoscope.
Single Head Stethoscope
The Single head stethoscope is preferred by Cardiac Specialists
for monitoring heart sounds. It has a wide frequency range and
the internal dual tube lumen delivers a clear clean sound.
Preferred by cardiac specialists.
Sprague Rappaport Stethoscope
Each earpiece is connected to the chest piece by its own tube, and these two tubes are held together by metal clips. The two tubes can rub together to create noise.
This scope looks dramatic but is getting less popular.
Acoustic stethoscope have poor amplitude and horrible fidelity. However, most electronic stethoscopes are cheap amplified implementation of the acoustic stethoscopes. Their high price is not justified by the low material cost.
The future belongs to a space age stethoscope using pressure sensors and advanced digital signal processing to deliver a loud clear sound.
Tunable corrugated diaphragms permit you to hear high and low frequency sound without rotating the device. The user applies light pressure for low sounds and more firm pressure for high pitched sounds.
In practice, they are hard to use and may lose their effectiveness over time.
Pediatrics Sized Stethoscope
Smaller sizes stethoscope.
Typical diaphragm 35mm
Triple Head Head Stethoscope
These odd looking stethoscopes are rarely used.
Fetal stethoscope ("pinard")
The instrument is shaped like a listening trumpet and is placed
on the abdomen of a pregnant woman.
Steel chest pieces have to be machined precisely to hold the diaphragm in place. Stethoscopes rely on airtight seals to transmit sound The weight and width affects sound intensity
Stainless steel is the best, zinc alloys and aluminum are also used..
Steel chest pieces will be heavier.
Removable non-chill rims are standard.
The diaphragm is for examination of the chest and abdomen and measurement of blood pressure. It should be made from high quality PE compound film, a resin with high flexibility, and high fidelity with minimal susceptibility to deforming and aging, .
Typical sizes are 35mm for adult use 25mm for pediatric use and 45mm
for cardiac use.
Tunable diaphragms permit you to hear high and low frequency sounds without rotating the device.
The user applies light pressure for low sounds and more pressure for high pitched sounds.
The bell of the stethoscope is the cup shaped part opposite to the diaphragm. The bell transmits low frequency sounds more effectively. Deep cone-shaped bells work well.
Tubes are made in a single dip molding process with PVC(polyvinylchloride) . Thin tubes can cause distortion, cause loss in the signal, and can pick up external noises.
The single tube splits into two separate tubes at the ear piece.
Two separate tubes directly connected with the ear pieces. Double tubes are more sensitive, but may rub against one another causing "squeaks" to be heard.
Bi-lumen designs are two internal bores incorporated into a single-tube design that eliminates noise artifacts created from two tube rubbing together. These are the ideal tubes in a good stethoscope.
Tube Length - Short vs. Long Tubing
There is only a small detectable difference in acoustical performance between stethoscopes with shorter tubing vs. those with longer tubing. Longer tubes drapes better around the neck, give more freedom when working with patients, and may reduce stress on the lower back while examining supine patients.
However shorter tubing brings you "closer" to the patient - adding the "human touch" factor.
Binaurals and Ear Tubes
Stainless Steel binaurals with inner spring binaural tubing assembly are better.
The headset assembly should be set at an anatomically correct angle (15 degrees). This assures a proper fit and minimizes air leaks.
Soft ear tips assure maximum comfort and excellent acoustical seal.
To reduce spring tension, hold each ear tube at the bend near the eartip and gradually pull apart until fully extended. To increase spring tension, grasp the headset with one hand where the ear tubes enter the plastic tubing and squeeze until the plastic tubing on one ear tube touches the other.
Use the proper sized ear tips - large or small for best performance.
The entire stethoscope can be wiped clean with alcohol or soapy water.
NOTE: Do not immerse your stethoscope in any liquid or subject it to steam sterilization. If disinfection is required, the stethoscope may be wiped with a 70% isopropyl alcohol solution.
Point the ear tips in a forward, not backward, direction as you place them in the ear canal.
Use light pressure (not excessive) when pressing the diaphragm on the patient.
Fully engage in either the diaphragm or bell position (dual head scopes).
Verify that the air passageway through the ear tips is not clogged.
Keep it Clean, hospitals and clinics are contaminated. So disinfect your stethoscope regularly.