When sound waves reach the ear, they are transformed into signals to the brain in the three different parts of the ear:
- The outer ear and the auditory canal
- The middle ear
- The inner ear
The outer ear and auditory canal are designed to amplify incoming sound waves. These then affect the eardrum, setting it into motion. Vibrations in the eardrum are transmitted to the hearing ossicles: the hammer, the anvil, and the stirrup, or malleus, incus and stapes. These tiny bones are in turn connected to the fenestra ovalis, which leads to the inner ear. As the eardrum is some 20 times larger than the fenestra ovalis, the vibrations are amplified. The fenestra passes sound waves on to the cochlea of the inner ear. Fluid contained in the snail shaped cochlea transmits the vibrations to the actual hearing organ, the organ of Corti. This organ contains more than 30,000 sensory cells, known as hair cells as they are equipped with "feelers". When these are agitated, the auditory nerve is affected, sending electrical impulses via nerve synapses to the hearing center of the brain.