The Outer Ear
Sound waves are collected by the outer ear (the portion visible on the outside of the head) and are funneled down the ear canal to the eardrum. The eardrum separates the outer ear from the middle ear space.
The Middle Ear
Sound waves cause the eardrum to vibrate. Behind the eardrum are three tiny middle ear bones. The eardrum vibration causes the middle ear bones to also vibrate. These tiny bones transfer sound to the inner ear.
The Inner Ear
Sound is passed to the inner ear via the vibrations of the middle ear bones. Fluid within the inner ear begins to vibrate which stimulates nerve endings called hair cells. The inner ear hair cells convert the vibratory signal into an electro-chemical signal which is then sent along the auditory nerve to the brain.
The brain is then responsible for interpreting the nerve impulses as sound and determines what is being heard (music, voice, background noise, etc).