The eardrum is a thin membrane that vibrates when incoming pressure waves strike it.

The longer version

A cone of skin and tissue stretched across the end of the ear canal moves in and out as arriving pressure swings push and pull on it. Its job is matching: it takes a large, loosely coupled movement in air and drives the much smaller, stiffer chain of bones behind it.

Area difference and lever action between the three tiny bones raise the pressure while shrinking the motion, which is what lets airborne waves enter fluid. A perforated drum leaks that pressure difference and dulls hearing until it heals. Muscles attached to the chain can stiffen it during very loud passages, trading sensitivity for safety.

Where this entry sits

Sound and Music gathers facts about how vibrations move through air and water, how ears turn them into meaning, and how instruments and notation shape what listeners hear. Expect echoes, pitch, volume, acoustics, and the odd silence in between. The full list sits on the Sound and Music page, where every entry is listed in order.