How Our Ears Hear

The human ear is divided into three parts – the outer ear, the middle ear, and the inner ear.
Each part has a separate function. The outer ear is the visible part of the ear, and its purpose is to direct the sound further inside. The outer ear ends where the eardrum starts.
The area after the eardrum is the middle ear, which ends at what is known as oval window.
The middle ear has three bones so small they can be placed together on a penny. These three bones are called stapes, malleus and incus (also called the anvil, hammer, and stirrup).
The sound waves that enter the outer ear make the eardrum vibrate. These vibrations are picked up by the three bones, which actually form a bridge.
The last bone, the stapes, transmits the vibrations to the oval window. The middle ear is the place where the sound gets amplified.
The sound transmitted to the oval window moves into the inner ear, a network of fluid-filled passages and tubes that run through the temporal bone of the skull. This network is often referred to as the bony labyrinth.
Movement of the fluid in the inner ear causes changes in tiny structures called hair cells.
Hair cells near the wide end of the snail-shaped cochlea detect higher-pitched sounds, such as an infant crying. Those closer to the center detect lower-pitched sounds, such as a large dog barking.
This movement of the hair cells sends electric signals from the inner ear up the auditory nerve. The auditory nerve carries this electrical signal to the brain, which turns it into a sound that we recognize and understand.