What is the purpose of these three bones in the ear

Question

http://members.aol.com/tonyjeffs/pics/ossicsm.gif

http://members.aol.com/tonyjeffs/pics/movie.gif

Answer 1

After sound waves hit the eardrum they stimulate the hammer which in turn stimulates the anvil and stirrup. They stimulate the cochlea. The Cochlea is lined with tiny hairs that then translate the vibrations into electrical signals via nerves. So in short. They are what allow you to hear.

Answer 2

They act as an "organic amplifier."

Answer 3

Impedance matching. They are a system of levers that change the relatively large-area, large-amplitude, low-pressure vibrations of the eardrum to the smaller-area, smaller-amplitude, higher-pressure vibration needed by the cochlea. The ref. estimates the pressure gain to be about 33 dB at 1 kHz.

Answer 4

They're a chain for processing sounds.  This tri-boned system is only found in mammals, and it processes Good Vibrations and other hits by the Beach Boys more efficiently than the single-boned middle ear of other vertebrates.  It's more flexible and, thus, more sensitive.

In terms of evolutionary history, the malleus is derived from a non-mammalian bone called the articular, the incus is a descendant of something called the quadrate, while the stapes is the original sound processor still doing the same job.  The first two mentioned used to form a jaw-skull joint a couple of hundred million years ago.  They'd gotten involved in sound processing while still operating as the jaw joint tens of millions of years earlier in non-mammalian cynodonts, the ancestors of mammals.