The operation of a normal ear

Sound, a wave phenomenon, causes the eardrum starts to move (oscillate). This causes the bones in the middle ear (hammer, anvil and stirrup) in turn driven. The stirrup brings this vibration on the cochlea (cochlea). The middle ear, the hammer, anvil and stirrup, makes sure that actually sounds without too much loss of energy, converted into a vibration of the fluid in the cochlea (the cochlea).

 

The various bones in the middle:

 

2 = anvil 1 = hammer 3 = stirrup

 

One problem is that the incoming sound to go on an air medium to a liquid medium. Exists a large degree of impedance or resistance, a loss of energy, here a loss of intensity.

To address this issue now as much as possible to face the middle ear acts as a impedantieaanpasser.
This is because the middle ear is structured as follows:

• the surface of the footplate of the stapes is much smaller than the eardrum, the pressure on the fluid in the inner ear is thus 30 times as large as the sound pressure on the eardrum.
• exists a tonic effect on the leverage of the ossicles, the movement of the oval window is smaller, but the force exerted is greater.

The mechanical vibrations of the middle ear are transmitted to very fine hair cells in the inner ear. Because these hair cells move creates voltage differences, which in turn lead to discharge volleys in many nerve fibers. The collective signal is ultimately via the auditory nerve to the brains forwarded.