The stethoscope was invented in France in 1816 by René Laennec at the Necker-Enfants Malades Hospital in Paris. It consisted of a wooden tube and was monaural. Laennec invented the stethoscope because he was uncomfortable placing his ear on women’s chests to hear heart sounds.:186 He observed that a rolled piece of paper, placed between the patient’s chest and his ear, could amplify heart sounds without requiring physical contact. Laennec’s 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”. Laennec called his device the “stethoscope” (stetho- + -scope, “chest scope”), and he called its use “mediate auscultation”, because it was auscultation with a tool intermediate between the patient’s body and the physician’s ear. (Today the word auscultation denotes all such listening, mediate or not.) The first flexible stethoscope of any sort may have been a binaural instrument with articulated joints not very clearly described in 1829. In 1840, Golding Bird described a stethoscope he had been using with a flexible tube. Bird was the first to publish a description of such a stethoscope but he noted in his paper the prior existence of an earlier design (which he thought was of little utility) which he described as the snake ear trumpet. Bird’s stethoscope had a single earpiece.
In 1851, Irish physician Arthur Leared invented a binaural stethoscope and, in 1852, George Philip Cammann perfected the design of the stethoscope instrument (that used both ears) for commercial production, which has become the standard ever since. Cammann also wrote 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.