The stethocope was invented in 1816 by Rene Laennec. The recorded history suggests that he was concerned about placing his ear against the breasts on young French women, and therefore sought an alternative. He tried a makeshift tube and found it to be a superior device. Laennec then wrote a book on auscultation, and the examination technique was widely adopted.
Modern stethoscopes are extensions of the basic idea, with tubing to conduct sound to the listener's ears.
Electronic stethoscopes are becoming more popular, and it is expected that these will replace mechanical devices within the next few years.