The modern stethoscope is made up of a Y-shaped flexible plastic tube. An earpiece is attached to each end of the Y and a sound-detecting device at the other end. The sound-detecting device has a thin plastic sheet on one side and a bell shape with a hole in on the other. The diaphragm is used to listen to a patient's chest for high-pitched sounds. The bell end is used to detect lower-pitched sounds. The lung sounds have a higher frequency than heart sounds.
Rene Theophile Hyacinthe Laënnec (1781-1826) was a French physician who, in 1816, invented the stethoscope. Using this new instrument, he investigated the sounds made by the heart and lungs and determined that his diagnoses were supported by the observations made during autopsies.