The Ideal Stethoscope delivers a clear loud sound, is comfortable, and looks good.  However, the only true test is what you actually hear.

Avoid the following

Stethoscope Types 

Dual Head

• Versatile general purpose device.
• Diaphragm mode for high frequency heart sounds
• Bell mode  for lower frequency lung sounds.
• Chest piece can be rotated.
• This is the most popular stethoscope.

 Single Head  

• Preferred by Cardiologists for monitoring heart sounds. 
• Has a wide frequency range
• Internal dual tube lumen delivers a clear clean sound.
  

 Sprague Rappaport 

• Each ear piece 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,

 Electronic stethoscopes 

• Acoustic stethoscope have poor amplitude and horrible fidelity. 
• Most electronic stethoscopes are essentially cheap amplifiers with a headphone.
• Their high price is not justified by the low material or design costs.
• A space age stethoscope with pressure sensors and digital signal processing is needed.

 Tunable ( corrugated diaphragms)

• 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

• Smaller sizes stethoscope.

  Fetal stethoscope (pinard)

• The instrument is shaped like a listening trumpet and is placed on the abdomen of the woman.

Chest Piece

• Steel chest pieces have to be machined precisely to hold the diaphragm in place.
• Stethoscopes rely on airtight seals to transmit sound.
• Steel chest pieces will be heavier. The weight and width affects sound intensity
• Stainless steel is the best, zinc alloys and aluminum are also used..
• Removable non-chill rims are standard.

Diaphragm 

• 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 cardiology.
• Tunable diaphragms permit you to hear high and low frequency sounds without rotating the device.

The Bell

• 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

                    

single tube              internal dual tube     

• 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..
• Bi-lumen designs are two internal bores incorporated into a single-tube design that eliminates noise artifacts created from two tube rubbing together.

Tube length - Short vs. Long Tubing

• Only a small detectable difference in acoustical performance. 
  
• 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 desirable.
• 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 ear tip 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.

Cleaning

• 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.

Usage Tips

•  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. Care Tips
•  Keep it Clean, hospitals and clinics are contaminated. So disinfect your stethoscope regularly.