A modern stethoscope, courtesy Huji, via Wikipedia
The stethoscope is a medical instrument used to amplify the sounds produced by the heart and lungs. It's of simple construction, consisting of a metal cone which is placed against the body which is connected to two flexible hollow hoses which have earpieces to insert in the physician's ear. Physicians must obtain a stethoscope in their first year of medical school and usually use the same one throughout their career. It replaced the solid wood or metal scope, where one end was placed against the patient and the other against the physician's ear. The stethoscope can therefore be used with the patient in any position.
Numerous types of lung sounds can be heard with a stethoscope. These sounds include wheezes, crackles, bronchial, and vesicular sounds. Lung sounds will sometimes be called breath sounds.
Physicians are trained how to use a stethoscope early in their careers. Despite the existence of much newer technologies, including ultrasound, and EKG, the stethoscope is still one of the physician's most important pieces of equipment. After only a little training, a physician can easily distinguish abnormal heart and lung sounds from those of a healthy patient.