Rene Theophile Hyacinthe Laënnec (1781–1826) was the one who invented the stethoscope.

He is a French doctor who worked in Necker-Enfants Malades Hospital in Paris.He found stethoscope because he was not comfortable placing his ears directly onto women’s chest to check the heartbeat rate.

Before the invention of stethoscope doctors were supposed to place their ears directly to the patient’s chest.In which rene feels uncomfortable with womens.
Story behind the stethoscope
One fine morning,walking on the street he was two children sending signals to each other using a piece of wood and pin.placing the one ear at the end of wood and in the other end a boy was scratching the pin.with an ear to end,the child received the amplified sound of the pin.this inspired him to invent the stethoscope.

I recalled a well known acoustic phenomenon: if you place your ear against one end of a wood beam the scratch of a pin at the other end is distinctly audible. It occurred to me that this physical property might serve a useful purpose in the case I was dealing with. I then tightly rolled a sheet of paper, one end of which I placed over the precordium (chest) and my ear to the other. I was surprised and elated to be able to hear the beating of her heart with far greater clearness than I ever had with direct application of my ear. I immediately saw that this might become an indispensable method for studying, not only the beating of the heart, but all movements able of producing sound in the chest cavity.-Dr.rene
This is the story behind the stethoscope.