How We Hear

The Anatomy of the Ear

Outer Ear

• Pinna (auricle) – collects and funnels sound into the ear canal
• Ear canal (external auditory meatus) – directs sound into the ear

Middle Ear

• Eardrum (tympanic membrane) – changes sound into vibrations
• Hammer, anvil and stirrup (malleus, incus and stapes) – this chain of three small bones (ossicles) transfers vibrations to the inner ear

Inner Ear

• Inner ear (cochlea) – contains fluid and highly sensitive "hair" cells. These tiny hair-like structures move when stimulated by sound vibrations
• Vestibular system – contains cells that control balance
• Auditory nerve – leads from the cochlea to the brain

How Hearing Works

• Sound funnels into the ear canal and causes the eardrum to move.
• The eardrum vibrates with sound.
• Sound vibrations move through the ossicles to the cochlea.
• Sound vibrations cause the fluid in the cochlea to move.
• Fluid movement causes the hair cells to bend. Hair cells create neural signals which are picked up by the auditory nerve. Hair cells at one end of the cochlea send low pitch sound information and hair cells at the other end send high pitch sound information.
• The auditory nerve sends signals to the brain where they are interpreted as sounds.