A stethoscope is a device that is used by doctors to listen to sounds created as the organs of the patient perform their tasks. The stethoscope is a flexible tube through which sound is transmitted by multiple reflections. One end of the stethoscope is inserted in the doctor’s ears and the other end which can either have a flexible diaphragm or be open is placed on the patient’s skin. Sound waves are created due to a pressure differential when the diaphragm is placed on the part the doctor wants to hear sounds from.
During multiple reflections of sound in the tube as the sound travels to the doctor's ear there is a small loss in amplitude. This is due to the fact that all materials absorb a part of the sound that falls on them and reflect the rest.
In spite of this, a stethoscope is a very useful instrument as the loss in loudness is relatively small. It is not possible for one to hear the sounds produced directly as the dispersion by air makes them impossible to hear.