It then strikes the eardrum, causing it to vibrate. This vibration causes the three tiny bones in the middle ear space to vibrate. The bones mechanically increase the sound pressure level as they conduct the sound through the middle ear space (normally filled with air) to the membrane at the entrance of the inner ear.
The inner ear is a fluid and membrane filled space hollowed out of bone in the skull. As the first membrane is vibrated, the inner ear fluid starts to move, causing movement of another membrane that has tiny nerve endings attached. This converts the sound into an electrical impulse, which the nerve endings pass on to the auditory nerve. The nerve sends it to the brain for processing.