Download Sound Waves

Sound Waves
Over the next few weeks, we
will discuss…
•How We Hear
•Properties of Sound
•Using Sound
Sound Waves
•How We
Hear

Answer the following
questions as you watch:
1. What three bones are found
inside your ear?
2. What does my body do that
allows me to hear?
3. What happens to your
hearing if the hairs in your
ears die or become paralyzed?
4. What other factors might
cause hearing loss?
1) What are the three bones found inside
your ear?



Hammer
Anvil
Stirrup
hammer
anvil
stirrup
2) What does my body do that allows me to hear?
1. A sound wave is FUNNELED through the
outer ear into the middle ear canal
2. The eardrum
vibrates and
AMPLIFIES the sound
when the wave hits it
(The eardrum is a
membrane that
stretches across the ear
like a drumhead)
3. These vibrations are transmitted to the
three small bones: the hammer,
the anvil and the stirrup
4. These bones AMPLIFY the sound
and send the energy to the inner ear
5. Hair tipped cells inside the
vibrate, GENERATE
SIGNALS containing information of the
sound and send them to the brain
cochlea
6. The brain INTERPRETS these
signals as sound to tell you about
the pitch, volume and length of the
sound you have heard
3) What happens to your hearing if the hairs in
your ears die or become paralyzed?
▪ You go deaf!
Wait… what
did you say?
4) What else might cause hearing loss?
 Exposure to loud sounds 33.7%
(leading cause of hearing loss)
– Constant exposure to loud noise can
damage hair cells in cochlea
 Old age 28%
– Higher frequencies are easily lost
– Sounds appear distorted
–
–
Sounds such as “s,” “f,” “sh,” “ch” are hard to hear
30% of people over 65 have some hearing loss to
aging
 Infection / Damage / Injury to ear 17%
Disease/sickness
 Other 16.8
– Mammals cannot make new
hair cells
 Born with hearing loss 4.4%
The AMPLITUDE! – The amount of
energy, The louder the sound, and the
longer you listen to it, the more
hearing you will lose!



The intensity of a sound is how much
energy passes through a given
area/distance in an amount of time
Loudness is the perception of how much
energy a sound wave carries
– The amount of energy
carried by sound waves is
described by a scale
called The Decibel Scale
o
o
o
o
o
0 dB = Threshold (softest sound we can hear)
15 dB = Whisper
20 dB = Cat purring
60 dB = Normal talking
85 dB = Noisy lunchroom
(prolonged exposure can cause damage)
o 110 dB = Lawn mower/Hair dryer
o 115 dB = iPod at peak volume
o 120 dB = Pain threshold
o 150 dB = Jet plane taking off
 At the human threshold, the
eardrum moves 1 billionth of a cm!
Hearing Loss Facts
•
Hearing damage begins to occur at 85
dB
– Some rock concerts produce sound levels
as high as 120 dB!
– iPod volumes peak at 115 dB
•
Amount of damage depends on
intensity of the sound and the length
of time that a person is exposed to it
Sound Waves
•Properties of
Sound
Sound Waves
• Sound waves are mechanical waves
that require a medium to travel and carry its
energy.
– Sound can’t travel in a vacuum like in outer space
because there are no particles to carry the energy.
• The type of mechanical wave sound is, is a
longitudinal wave.
– “Sound waves are longitudinal”
– Many machines that measure sound use a transverse
wave picture to show the sound wave properties of
amplitude and wavelength because it is easier.
• Compression = crest
• Rarefaction = trough
Frequency
• The number of complete waves that pass a given point
in a certain amount of time
• Frequency is measured in units called “Hertz”
– 1 Hertz is equal to 1 wave per second
– 100 Hz is equal to 100 waves per second
High Frequency
Low Frequency
•
Pitch is how high or low a sound is, and it
corresponds with the sound’s frequency
–
–
High pitch sound waves have shorter wavelengths
Lower pitch sound waves have longer wavelengths
High pitch
Low pitch
–
Detectable Sounds
– Human ear detect sound waves 20
Hz - 20,000 Hz
– Dogs hear frequencies up to almost
50,000 Hz
– Dolphins and bats hear as high as
150,000 Hz
Mythbusters Video
“Breaking Glass”
• In this video, Adam and Jaime try to test
the myth that a singer can break glass
using only their voice.
Sound Waves
•Using Sound
The Doppler Effect: The change in frequency
that occurs when a source of sound is
moving relative to a listener
•
•
Pitch is affected as an object moves
towards you, then away from you
Sound spreads out as it travels
– Object moves towards you
making sound waves compress:
results in higher pitch
– As the object moves away from
you, sound waves spread apart:
resulting in lower pitch
•
•
Ex: Radar guns – measure speeds of cars/baseball
pitches
The radar gun uses the change in frequency of the
reflected wave to determine the object’s speed
– Sound waves are emitted by an animal, hit an
object and reflect back towards the source,
which allows the animal to navigate, hunt,
and communicate
• Bats: Emit high pitched squeaks to determine
placement in time/space, locate food or other
objects
• Dolphins: Use high-pitched clicks to navigate
• Humans: Use ears to interpret echoes (to
estimate size/shape of room)
–
–
High-frequency sound waves above 20,000 Hz
reflect off body structures, and the resulting
“echo” is then sent to a computer, that receives
these reflected waves and makes images of the
structure
•
•
Examine developing fetus
Examine internal organs
– Alternative to surgery – focusing
sound waves on kidney stones or
gallbladder stones can break them
up so that they may be safely passed
through the body
•
Extremely low
frequency waves
below 20Hz
emitted by
elephants that
allows them to
communicate over
long distances
–
The amount of time it
takes an echo to return
depends on how far
away the reflecting
surface is
Use sound waves to
map objects
underneath a body of
water
–
•
Used to map undersea
features, detect
submarines, schools of
fish and other objects