How Hearing Works

Did you know that the human body can hear faster than it can see, taste, smell, and feel?  Our ears truly are unique parts of our anatomy.

In order to better understand how hearing works, first we need to understand sound.  Simply put, sound is an air pressure fluctuation.  Whenever a car horn beeps, a person talks, a cat meows, or you hear any other noise, air particles near the source of the sound are pushed forward at a fast rate.  These air particles bump into other nearby air particles, causing a chain reaction.  Sound acts as a wave, with particles pushing on nearby particles, and so on.  This "sound wave" is what we are hearing.

The above animation shows a sound wave in action.

These sounds are heard because of our ear's unique design.

First, the outer part of our ear (also known as the pinna) collects sounds from all different directions.  The pinna works like a funnel allowing it to pick up sound in front of us better than behind us. The pinna funnels sound into our ear canal.

The ear canal is a long, narrow tube, often containing cerumen (ear wax) and tiny hairs.  At the end of the ear canal is the ear drum, also known as the tympanic membrane.  The ear drum is a very thin layer of skin that vibrates in response to the sound that comes into the ear.  Attached to the back side of the ear drum are three tiny bones called the malleus, incus, and stapes.

These tiny bones move when the ear drum moves, providing a significant boost to the sound level.  The tiniest bone (stapes) passes on the sound signal by pushing on a very special part of our inner ear, called the cochlea.  The cochlea is shaped like a snail's shell and is often referred to as the organ of hearing due to its importance.

Inside the cochlea are thousands of tiny sensors called outer hair cells.  Each of these tiny cells are responsible for sensing different pitches of sound.  These outer hair cells will move slightly when their sound moves across them.  When an outer hair cell moves, it sends a message to the brain to notify it of a sound.  The message is sent using the auditory nerve, which connects the cochlea with the brain.  That is how the hearing system works!

A common misconception about hearing is that we hear with our ears. But, in reality, our ears only act as satellites and pick up the sound.  It is our brain that makes sense of the sound.