Transcript File

29/03/2016
Sound and Hearing
Investigating Sounds
Put your hand on your throat and
talk. What can you feel?
ALL SOUND IS
CAUSED BY
VIBRATIONS!
Your throat VIBRATING.
Put your hand on a loudspeaker that is
producing sound. What can you feel?
The loudspeaker VIBRATING.
Strike a tuning fork against a wooden block. What can you see?
The prongs of the tuning fork VIBRATING.
Place a ruler half over the end of a table and flick the ruler. What
can you see?
The ruler VIBRATING.
Pluck a string on an instrument. What do you see?
The
string VIBRATING.
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Sound and Vibrations
All sound is caused by VIBRATIONS.
How does sound travel from a vibrating
object to your ear?
The vibrating object makes the AIR
PARTICLES VIBRATE.
The vibrations are passed along from
air particle to air particle in the form of
Sound travels in waves.
WAVES.
The air particles make your EAR DRUM vibrate.
Your ear drum makes three small bones, called OSSICLES, vibrate.
These are connected to your COCHLEA that contains thousands of
SMALL HAIRS. These small hairs DETECT the vibrations.
The AUDITORY NERVE carries messages to your BRAIN which
are interpreted
as SOUNDS.
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How sound travels…
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As we know, sound waves are formed when something vibrates.
But how does the sound reach our ears?
Air molecules
1) An object
makes a
sound by
vibrating
2) The vibrations pass
through air by making
air molecules vibrate
3) These
vibrations are
picked up by
the ear
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Travelling sound
Sound travels by particles vibrating. To understand this
better you need to remember what the particles look
like in a solid, liquid and a gas:
solid
liquid
gas
Which state does sound travel fastest through? Why?
In
whichtravels
state are
the particles
closest
together?
solid
Sound
fastest
through solids
because
the particles
are closer together than in a liquid and a gas, so the
vibrations
are are
more
passed
fromapart?
particle to particle.
In
which state
theeasily
particles
furthest
gas
Speed of sound
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The speed of sound in air is around 330 m/s. What happens
when sound travels through different materials?
Speed of
sound
(in m/s)
5000
4000
3000
2000
1000
0
Air
Water
Brick
Iron
Conclusion – the denser the material, the
faster sound travels through it
Material
Making Sounds
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A sound is made when an object or material VIBRATES.
Take, for example, a guitar.
To make a sound with a guitar a string has to
vibrate. We can raise the pitch of the sound
a guitar makes by doing three things:
1) _________ the length of the string
2) _________ the string
3) Using a _________ string
We can make the sound louder by ________ the string harder
Words – tightening, thinner, increasing, plucking
Sound and Vacuums
Sound can travel
through solids, liquids
and gases.
SOUND CAN NOT
TRAVEL THROUGH
A VACUUM.
If you were in space
you would not be able
to talk as there is NO
AIR TO VIBRATE.
If you were in space
and there was an
explosion you would
not be able to hear it.
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The Bell-jar experiment
What happens when the air is removed from the bell-jar?
 Sound waves are vibrations and so need a substance
to travel through.
 With air inside, the sound can be heard.
With nothing inside [a vacuum], the sound can’t be heard.
© Boardworks Ltd 2003
Parts of the Ear
Oval
window
Ossicles
Semi-circular
canals
Auditory
nerve
Ear drum
Pinna
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Cochlea
Eustachian
tube
Loudness and Distance
The FURTHER AWAY
a sound is, the
QUIETER a sound is.
I can’t hear
it - it’s too
quiet!
What
beautiful
music!
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Effects of Noise
What is NOISE?
A NOISE is UNWANTED SOUND.
What sorts of noises could damage your hearing?
Loud music.
Machinery.
Explosions.
Aircraft.
How can you protect yourself from loud noises?
Ear protectors.
NAUSEA
Double glazing.
WhatHEADACHES
are the effects of
noise on your body?
LOSS OF HEARING
Putting machinery into separate
rooms to workers.
Turning
down the volume of music.
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DEAFNESS
How does the ear work?
1) Sound waves
are “funnelled”
into the ear by
the pinna
2) These
vibrations
make the ear
drum vibrate
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5) The electrical
signals are then
sent to the brain
3) These vibrations make
the ear bones vibrate
4) These
vibrations are
turned into
electrical
signals in the
cochlea