The stethoscope is an acoustic medical device for auscultation, or listening to the intenal sounds of body. It is used to listen to lung and heart sound. When combination with a sphygmomanometer. It can listen to bloodflow in arteries and veins. "Mechanic's stethoscopes" are used to listen intenal sound made by machines, such as automobile engine.
The stethoscope was invented in France in 1816 by René Laennec the Necker-Enfants Malades Hospital in Paris. It consisted of a wooden tube and was monaural. His device was similar to the common ear trumpet, a historical form of hearing aid indeed, his invention was almost indistinguishable in structure and function from the trumpet, which was commonly called a "microphone".
In 1851, Arthur Leared invented a binaural stethoscope, and in 1852 George Cammann perfected the design of the instrument for commercial production, which has become the standard ever since. Cammann also authored a major treatise on diagnosis by auscultation, which the refined binaural stethoscope made possible. By 1873, there were descriptions of a differential stethoscope that could connect to slightly different locations to create a slight stereo effect, though this did not become a standard tool in clinical practice.
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