How your hearing works

Ear anatomy

ear-anatomy-diagram

Your ear consists of 3 parts:

Outer ear: the visible outer portion of the ear and ear canal.

Middle ear: the eardrum and three tiny bones.

Inner ear: the fluid-filled cochlea, which contains thousands of tiny sound receptors called hair cells.

FOR PEOPLE WITH NORMAL HEARING, sound passes through all three parts of the ear. The outer ear collects the sound and directs it to the eardrum, causing it to vibrate. This vibration creates a chain reaction in the three tiny bones of the middle ear.

movement-of-bones-inside-ear Motion of these bones causes fluid to move throughout the inner ear, or cochlea. As the fluid moves, thousands of tiny sound receptors that line the cochlea bend back and forth. When the hair cells move, they send electrical signals to the hearing nerve, which carries them to the brain where they are interpreted as sound.

Our brain interprets these signals and tells us in turn that the doorbell rang, or that words are being spoken. Many things help determine just exactly what it is you hear, but it is the combination of frequencies that give different sounds their distinctive qualities – you will understand why this statement is so fundamental to your hearing later in the book. Source and direction of the sound and loudness are other clues the brain uses to decipher messages.