The Ear and Hearing

1
The Ear and Hearing
2
If a tree falls in an empty forest, is there a
sound?
3
To answer this question, one must first define
sound.

• What is sound?
• Discuss for two minutes. . .

4
Sound Definition

• The transmittance of vibration through matter.
  The medium varies --water, air, walls of stone, a
  creaking floor. Sound transmits to a receiver
  that can interpret these signals as information.

5

• Sound moves through air similar to the way
  ripples in a pond move through water.

6
What is a Sound Wave?

• Sound waves come in various frequencies and
  amplitudes, just like ocean waves come in
  different rates and heights.
• Faster frequencies are higher tones, slower
  frequencies are lower tones.
• Higher amplitudes (height) are louder, lower
  amplitudes are quieter
• Your ear can sense some of these infinite ranges,
  but not all of them other animals have
  different ranges of frequency that they can hear.

7
High and Low Pitched Sound
8
(No Transcript)
9
Loud and Quiet

• Amplitude relates to loudness
• Loudness is measured in decibels

10
(No Transcript)
11
(No Transcript)
12

• Section B here, Monday

13
There Are Three Main Parts to the Ear

• Outer filled with air
• Middle filled with air
• Inner filled with water

14
The Outer Ear

• The Outer Ear includes the Pinna, the Ear Canal
  and the Tympanic Membrane (Ear Drum).

Ear Canal
15
Pinna
Function The outermost part of the ear is
called the pinna or auricle (say or-ih-kul).
This is the part of the ear that people can see.
It collects sound waves
16
Form Follows Function

• This Spy Microphone is designed to catch sound
  waves. How is it similar to how your pinna has
  evolved?

17
(No Transcript)
18

• The outer ear includes earwax. Earwax is that
  gunky stuff that protects the canal. Earwax
  contains chemicals that fight off infections that
  could hurt the skin inside the ear canal. It also
  collects dirt to help keep the ear canal clean.

19
The Middle Ear

• The middle ear's main job is to take the sound
  waves you hear and turn them into vibrations that
  are delivered to the inner ear.
• Sound waves enter the outer ear, they travel
  through the ear canal and make their way to the
  tympanic membrane, or eardrum, a thin piece of
  tissue stretched tight like a drum.
• The eardrum vibrates with the sound, and pushes
  the three bones of the middle ear. (the ossicles)
• This turns sound waves into mechanical movement,
  like the straw and ping-pong ball.
• The ossicle motion pushes against the fluid of
  the inner ear, turning the motion into waves in
  water.

20
(No Transcript)
21
Ossicles

• The eardrum separates the outer ear from the
  middle ear and the ossicles (say ah-sih-kulz).
• What are ossicles? They are the three tiniest,
  most delicate bones in your body.

22
The Three Bones!

• the malleus, or hammer
• the incus, or anvil
• the stapes, or stirrup
• Together, these work as a lever.
• They are pushed by the eardrum and they push
  against the inner ear.

23
(No Transcript)
24
Ear Animation .. .

• http//www.infj.ulst.ac.uk/pnic/HumanEar/Andy's2
  0Stuff/MScProject/workingcode_Local/RunTest.html

25
Review

• How does sound move from outside your ear to the
  inner ear, and what ear parts are involved?
• Take 5 minutes to figure this out with your
  partner.

26
The Inner Ear Nerve Signals Start Here

• Sound comes into the inner ear as vibrations from
  the ossicles and enters the cochlea (say
  ko-klee-uh), a small, curled tube in the inner
  ear.
• The cochlea is filled with liquid, which is set
  into motion, like a wave.

27
(No Transcript)
28

• The cochlea is lined with tiny cells covered in
  tiny hairs that are so small you would need a
  microscope to see them.
• When sound reaches the cochlea, the vibrations
  cause the hairs on the cells to move, creating
  nerve signals that the brain understands as
  sound.

29
(No Transcript)
30
(No Transcript)
31
How is Seaweed like hair in the cochlea?
32
Damage to your ability to hear . . .

• The hairs in your cochlea are connected to
  nerves. When there is too much vibration, like at
  a rock concert, theses hairs can be damaged and
  even break off, never to be replaced. (You cannot
  grow new hairs.) This is like a storm tearing
  seaweed from the ocean floor during a storm.

33
Day or Night, Ears Keep You Upright

• Ears do more than hear.
• They keep you balanced, too. In the inner
  ear, there are three small loops above the
  cochlea called semicircular canals. Like the
  cochlea, they are also filled with liquid and
  have thousands of microscopic hairs. When you
  move your head, the liquid in the semicircular
  canals moves, too. The liquid moves the tiny
  hairs, which send a nerve message to your brain
  about the position of your head. Almost
  immediately, your brain sends messages to the
  right muscles so that you keep your balance.

34
Popping Ears?!?
35
Eustachian Tubes
Eustachian tubes equalize the pressure between
the space in your head and the outside world.
What would happen if it were to become clogged
with mucus?
36

• http//kidshealth.org/kid/body/ear_noSW_p3.html
• http//hyperphysics.phy-astr.gsu.edu/hbase/sound/i
  mgsou/eari2.gif
• http//faculty.concord.edu/rockc/intro/img009.jpg