The first stethoscope was devised by René Laennec in 1816. It consisted of a wooden tube about 30cm long and 3 cm in diameter. This was a monaural device; that is, the doctor listened to the heart or chest with one ear. Over the next few years, following the publication of his book on mediate auscultation and its translation into English by John Forbes in 1821, there were other variations on the monaural stethoscope.
One monaural stethoscope that is still used is that devised by Adolphe Pinard and used to listen to the foetal heart.
The first binaural stethoscope was devised in 1851 by Arthur Leared and a wide variety of binaural stethoscopes followed. The next big advance occurred in the 1940s when the Sprague-Rappaport dual-head stethoscope was devised. This consisted of a bell end and a flat diaphragm that allowed the doctor to listen easily to high and low-pitched sounds.
An improvement on this was the Leatham stethoscope with a very shallow diaphragm (disc) and a double bell/cup, first described in 1958. This rather heavy instrument was replaced in the 1960s by the Littmann stethoscope which was much lighter and easier to use.
The next improvement was the electronic stethoscope which essentially uses a microphone and transmitter and enables magnification of the heart and breath sounds.
The last – and perhaps final – form of the stethoscope is the Doppler stethoscope that uses the effect of sound waves reflected off objects. It has been in use for foetal heart examination for many years but is now becoming used for the heart.