The Human Ear
Humans and other animals have ears to
detect sound waves. In the most primitive sense, they are meant to
alert us of predators or a possible meal. Then we took advantage of
our ears, and learned to communicate through speech and music.
The human ear consists of three main
parts; the outer ear, the middle ear, and the inner ear. The outer
ear consists of: the pinna, the ear canal, and the eardrum. The
pinna is the cartilage flap that is visible, and acts as a funnel to chorale
the sound waves through the ear canal to the eardrum. To hear more
sound, you can cup your hand over your ear in the shape of a larger funnel.
Once the sound wave reaches the eardrum, it is transferred
to the inner ear via the middle ear which consists of; the three smallest
bones in the human body called the hammer, anvil, and stirrup, and also
the eustachian tube which equalizes the pressure on the eardrum to compensate
for atmospheric pressure. The eardrum vibrates, which causes the bones
in the middle ear to vibrate. This action transmits the information to
the inner ear.
When the sound reaches the inner ear, it is changed
from a longitudinal wave into electrical signals that can be processed
by the brain. To do this, the stirrup vibrates against a small tissue
called the cochlea. This is filled with an endolymph fluid. The
vibrating fluid causes tiny hairs, called cilia, to vibrate at the same
frequency as the endolymph fluid. The cilia are then able send that
information to the brain using electrical signals through the auditory nerve..
So why do our ears ring after a prolonged
period of loud noise?
Like any other object, the cilia
in the ear have resonant frequencies. When the cilia resonate at their
resonate frequency for a long period, the get damaged and die. The
ringing sensation is the signal that is produced from a dying cilia. The
cilia never grow back, so it is best to keep this from happening.
To prevent this from happening, it is best to reduce the amount of loud
noise that enters the inner ear. The most common way this is done
is by using ear plugs when exposed to loud noises.
This animation shows how an incoming sound wave
interacts with the ear drum and causes it to vibrate.
After this point, the sound wave is no longer in longitudinal form.
It is transferred to the brain using electrical signals.
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