1. 09/11/2018
Sound and Hearing

2. ALL SOUND IS CAUSED BY VIBRATIONS!
Investigating Sounds
ALL SOUND IS CAUSED BY VIBRATIONS!
Put your hand on your throat and talk. What can you feel?
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.
09/11/2018

3. 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 WAVES.
Sound travels in 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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4. How sound travels…
09/11/2018
As we know, sound waves are formed when something vibrates. But how does the sound reach our ears?
Air molecules
2) The vibrations pass through air by making air molecules vibrate
3) These vibrations are picked up by the ear
1) An object makes a sound by vibrating

5. Travelling sound
09/11/2018
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 which state are the particles closest together?
Sound travels fastest through solids because the particles are closer together than in a liquid and a gas, so the vibrations are more easily passed from particle to particle.
solid
In which state are the particles furthest apart?
gas

6. Speed of sound
09/11/2018
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)
Material
Conclusion – the denser the material, the faster sound travels through it

7. Making Sounds A sound is made when an object or material VIBRATES.
09/11/2018
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

8. 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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9. 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.

10. Parts of the Ear Oval window Semi-circular canals Ossicles
Auditory nerve
Ear drum
Cochlea
Pinna
Eustachian tube
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11. 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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12. What are the effects of noise on your body?
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
HEADACHES
LOSS OF HEARING
DEAFNESS
Double glazing.
What are the effects of noise on your body?
Putting machinery into separate rooms to workers.
Turning down the volume of music.
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13. How does the ear work?
09/11/2018
1) Sound waves are “funnelled” into the ear by the pinna
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
2) These vibrations make the ear drum vibrate