How We Hear
Ever wonder how sounds in our environment reach our ears?
How does noise cause damage to our ears?
What makes some sounds dangerous while others are not?
For better protection against damage-causing noise, it’s important to first understand how we hear.
The Path of Sound
There are three main parts of the auditory system: the outer, middle and inner ear.
Sounds from our environment travel through these three parts of the auditory system, setting off a chain reaction to finally reach the brain, where they are then heard and interpreted.
In order for sounds to be heard, all parts of the ear need to function effectively.
Phase 1: Sound Waves Reach the Ears
Sound waves are trapped by the pinna (the fleshy outer portion of the ear) and travel a winding path around and down through the ear canal.
Phase 2: Vibration
The eardrum, or tympanic membrane, is located at the end of the ear canal. When sound waves reach the eardrum, it responds by vibrating. This vibration is then transferred to three small bones in the middle ear - the malleus, incus and stapes (also know as hammer, anvil and stirrup.)
Phase 3: Amplification
The bones amplify the incoming sounds, passing them along to the cochlea, a small, snail-shaped organ located in the inner-ear that is filled with fluid and lined with 15 to 20 thousand small hair cells.
Phase 4: Pressure
Once sound reaches the chochlea, a pressure wave is set into motion. A traveling wave moves through the cochlea and excites the hair cells.
Phase 5: Reception & Processing
Activated hair cells create an electrical impulse that passes the information on to the brain via the auditory nerve. The brain then interprets, or processes, what is heard so we can understand and react to what we hear.