What is a stethoscope?


The stethoscope is an instrument that enables doctors and other health care professionals to listen to the function of various parts of the body such as heart and lungs. The technique behind the stethoscope was first reported by Leopold Auenbrugger in the 18th century. He used the method of tapping on the chest (percussion) to detect diseases of the lungs and heart. The idea of percussion or tapping came to him after observing his father tapping on wine barrels to determine the levels of the liquid in them.


Réné Laännec is credited with inventing the stethoscope in 1816. As a medical practitioner he realized that sometimes, in case of overweight patients, it was impossible to hear any heartbeat or lung sounds. He used the idea of a rolled up paper as an ear trumpet to successfully listen to the heart and lungs of these patients. In 1819, Laännec published a book in which he described a wooden stethoscope he had constructed.

The Stethoscope Today

The modern instrument consists of a small funnel or a hollow drum attached to a forked rubber tube. Two earpieces are attached to the other ends of the fork. The doctor can listen through the ear-pieces by placing the drum or the funnel on the chest cavity. The use of the stethoscope in the early years was limited to studying the heart and lungs. In modern times, it is also frequently used for detecting the pulse in the arm, and also for investigating abnormalities in the gastrointestinal tract.

Applications & Use

The stethoscope takes advantage of the fact that the lungs, heart, and other organs are situated in specific body cavities that can expand or deflate during the breathing process. The lungs are located in the chest cavity that is surrounded by the ribs and the diaphragm. When a person is breathing in, the diaphragm is lowered and the rib-cage is expanded. Air then flows into the lungs to take up the extra space. These changes can be picked up by the stethoscope. In the case of diseases that are responsible for accumulation of fluid in or around the lungs or heart, the clear hollow sound is replaced by a dull thud and/or crackling sounds.