Anvil

three tiny bones are missing. put them back.

an ear cut open with its three bones missing: drag each one home, and the same tap goes from silent to loud

Sound arrives at your eardrum as a big, soft push spread over about 55 square millimetres, and it has to end up moving fluid inside the cochlea, which is far harder to push than air. Three bones do that conversion: the hammer and anvil rock together about a single pivot, which gives roughly a 1.3x lever, and the stirrup concentrates the force onto an oval window of only about 3.2 square millimetres, roughly a 17x area ratio. Multiplied, that is about a 22x pressure gain -- near 27 decibels -- which is why breaking the chain costs roughly 25 to 30 decibels of hearing and why the same tap here goes nearly silent when you pull a bone out.

Concepts: hearing, anatomy.

An interactive you play with one thumb, on Wundr.