How Do We Hear?
Hearing is the sensing of sound vibrations in the air. When a sound occurs (people speaking, doorbell, birds chirping, music) it produces a vibration that travels through the air displacing it. The displaced air is called a sound wave. Sound waves are collected by the outer ear and delivered to the ear drum, which vibrates at different rates depending on the pitch of sound. This vibration in turn sets the three tiny bones (the middle ear "ossicles") into motion, transmitting the ear drum vibrations down to the inner ear (cochlea). The cochlea is a hollow bone, filled with fluid and tissue holding thousands of tiny "hair cells". As vibrations enter the cochlea, the hair cells lining the inside of the cochlea move in response. When the hair cells "bend", they send neural impulses (or electrical signals) to the hearing (auditory) nerve. The auditory nerve from both ears will travel up to the brainstem, and then finally to the brain (in the auditory cortex).
We Hear With Our Brain!
Many people think we only need our ears to hear, but it is important to remember "we hear with our brains." Our outer, middle, and inner ear provide a way for sound to be transmitted to the brain. The brain itself (from the auditory nerves, to the brainstem, and then up to the auditory cortext) does a lot of work when it comes to "processing" sounds, to help us understand what we have heard.