The
Human
Ear
Definition: the
organ humans
use to detect
sound.
http://www.a3bs.com/3d_models.html
The human ear is divided into
three sections.
Each part of
the ear serves
a specific
purpose in the
task of
detecting and
interpreting
sound.
The Outer Ear
• Picture a satellite dish
that collects radio
waves.
• The outer ear is
similar!
– The curved formation on
the outside ( the pinna)
helps funnel sound down
the ear canal to the
eardrum.
The Middle Ear
• The middle
ear transfers
the energy
of a sound
wave by
vibrating the
three bones
found there.
Bones of the Middle Ear
• These are
Hammer
the smallest
bones in
your body!
• Together,
they’re
about the
size of an
orange
seed.
Eardrum
Anvil
Stirrup
The Stirrup (or stapes)
How Sound Travels in the
Middle Ear
• When sound waves
reach the middle ear,
they cause the
eardrum to vibrate.
• This vibration then
causes the three
bones to vibrate.
• These vibrations are
transformed into
longitudinal/pressure
waves in the middle
ear.
The
Inner
Ear
• Two main parts:
–Cochlea
–Auditory Nerve
The Cochlea
• Coiled like a snail
shell
• Contains
approximately
300,000 hair cells
• Is filled with
fluid, through
which sound can
travel easily.
Cochlear Hair Cells
• These tiny
hairs bend
because of
the
vibrations
caused by
the sound
waves.
Cochlear Hair Cells in Action
The Auditory Nerve
• The tiny hair cells
of the cochlea are
set in motion by
vibrations
• The vibrations
stimulate tiny
nerve cells.
• The nerve cells
then send signals
along the auditory
nerve to the brain.
A sound is
not
actually
heard until
the brain
receives
and
processes
these
signals.
Let’s start at the
very beginning…
• http://www.youtube.com/watch?v=CSO7
65hyxrc
Put the following steps in order:
A. The stirrup moves back and forth,
creating pressure waves in the
cochlea.
B. The bones of the middle ear
(hammer, anvil, & stirrup) vibrate.
C. Hair cells send an electrical
impulse through the auditory
nerve.
D. The outer part of the ear (the
pinna) "catches" the sound waves.
E. Sound waves vibrate the eardrum
F. The brain receives an electrical
impulse and interprets it as sound.
G. Tiny hair cells in the cochlea move
as the waves pass.
H. The sound waves travel into the
ear canal.
D
H
E
B
A
G
C
F