You hear sounds when vibrations get inside your ears and stimulate your nerves to send electrical signals to your brain.

Suppose, for instance, that you are pounding on a drum. The drumhead starts vibrating. As the drumhead vibrates, it bumps into air molecules and starts them bouncing to and fro. Those bouncing air molecules bump into other air molecules and start them moving. This chain reaction of moving air molecules carries sound through the air in a series of pulsating pressure waves that we call sound.

Sound waves carry vibrations from the drum into your ears. Inside your ear, moving air molecules push on your eardrum and start it vibrating. Your eardrum, in turn, pushes on the bones of your middle ear, the tiniest bones in your body. These bones act like a set of levers, pushing against the thin membrane that covers the opening to your inner ear.