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KS3 Physics

8L Sound and
Hearing
1 of 36
20

© Boardworks Ltd 2004
2005
Contents

8L Sound and Hearing
What is sound?
Speed of sound
Reflecting sound
The ear and hearing
Summary activities
1 of ...
What causes sound?
Take a tuning fork and strike it
against a block of wood.
What do you observe?
The tuning fork vibrates...
Good vibrations!
What vibrates so that the following make sounds?
violin
strings

drum
skin

voice box
loudspeaker
cone
1 ...
The bell-jar experiment
Place a ringing clock inside the bell jar and what happens?
There is air inside the bell jar
so th...
Studying sound waves
Sound waves can be studied with this type of equipment.
loudspeaker
oscilloscope
signal generator

A ...
Loudness and amplitude
A sound can be quiet or loud.

quiet sound

loud sound

On an oscilloscope trace, the loudness of a...
Which is the loudest?
Which trace represents the loudest sound?

A

B

Sound A is the loudest.
Sound A has the largest amp...
Pitch and frequency
A sound can be high or low – this is the pitch of the sound.

low pitch sound

high pitch sound

On an...
Which is the highest?
Which trace represents the sound with the highest pitch?

A

B

Sound B is the highest
pitched.
Soun...
Wave animation

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11 of 36

© Boardworks Ltd 2004
2005
Contents

8L Sound and Hearing
What is sound?
Speed of sound
Reflecting sound
The ear and hearing
Summary activities
1 of ...
Speed of sound experiment
This investigation to calculate the speed of sound should
be carried out in a quiet open space.
...
Speed of sound experiment – results table
Record the results of the sound experiment.
Experiment distance
(m)

1

100

tim...
Speed of sound experiment – results
The speed of sound in air is about…

340 m/s
Use the results of the cymbals experiment...
Sound in different states of matter
Sound needs a substance to travel through and travels by
particles vibrating.
Which st...
Speed of sound in different materials
Sound need particles to travel and the type of substance
affects the speed of sound....
Breaking the sound barrier!
Which of these travel faster than the speed of sound in air?

distance
(m)

time
(s)

speed
(m...
Sound or light – which is faster?
During a thunderstorm,
thunder and lightning are
created at the same time.
Which do you ...
Contents

8L Sound and Hearing
What is sound?
Speed of sound
Reflecting sound
The ear and hearing
Summary activities
1 of ...
Reflected sound
What happens when a sound wave meets a hard flat
surface?

The sound wave is reflected back from the surfa...
Echo experiment
Stand at least 100 m from a large, flat wall with a stop watch.

START

150 m

STOP
1. Use a starting pist...
Echo experiment
The sound of the starting pistol takes 0.92 s
to travel a distance of 300 m.
How can you use this result t...
Questions on reflecting sound
1. What is a reflected sound called?
an echo
2. Are hard or soft surfaces best at reflecting...
Contents

8L Sound and Hearing
What is sound?
Speed of sound
Reflecting sound
The ear and hearing
Summary activities
1 of ...
The ear and sound waves

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26 of 36

© Boardworks Ltd 2004
2005
How does the ear hear?
1.Sound waves are
collected by the
ear lobe or
pinna.

6.The auditory nerve
takes the signals
to th...
Hearing range
Set the volume and increase the frequency of the signal
provided by the signal generator.

Humans can only h...
Comparing hearing ranges
Which animals hear the lowest and the highest frequencies?
100,000
10,000
1,000
frequency
100
(Hz...
Hearing ranges and hearing loss
Does everyone have the same hearing range?
We all have slightly different hearing ranges
P...
Measuring loudness – the decibel scale
decibels

160
aircraft
overhead

personal stereo

140

permanent
ear damage

120
10...
Noise and its effects
A noise is any unwanted sound.
What one person considers noise another person might not.
Can you nam...
Contents

8L Sound and Hearing
What is sound?
Speed of sound
Reflecting sound
The ear and hearing
Summary activities
1 of ...
Glossary
amplitude – The height of a wave, which shows how loud
a sound is.

cochlea – The part of the inner ear that ch...
Anagrams

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35 of 36

© Boardworks Ltd 2004
2005
Multiple-choice quiz

1 of 20
36 of 36

© Boardworks Ltd 2004
2005
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8 l sound & hearing (boardworks)

  1. 1. KS3 Physics 8L Sound and Hearing 1 of 36 20 © Boardworks Ltd 2004 2005
  2. 2. Contents 8L Sound and Hearing What is sound? Speed of sound Reflecting sound The ear and hearing Summary activities 1 of 36 20 2 © Boardworks Ltd 2004 2005
  3. 3. What causes sound? Take a tuning fork and strike it against a block of wood. What do you observe? The tuning fork vibrates and you hear a sound. Sounds are made when an object vibrates. 1 of 36 20 3 © Boardworks Ltd 2004 2005
  4. 4. Good vibrations! What vibrates so that the following make sounds? violin strings drum skin voice box loudspeaker cone 1 of 36 20 4 © Boardworks Ltd 2004 2005
  5. 5. The bell-jar experiment Place a ringing clock inside the bell jar and what happens? There is air inside the bell jar so the sound can travel and be heard. vacuum pump on Remove the air from the bell jar and what happens to the sound? The sound cannot be heard because there is no air inside the bell jar (a vacuum). 1 of 36 20 5 © Boardworks Ltd 2004 2005
  6. 6. Studying sound waves Sound waves can be studied with this type of equipment. loudspeaker oscilloscope signal generator A loudspeaker converts signals from the signal generator into sound waves. 1 of 36 20 6 A signal generator produces different types of signals. An oscilloscope shows wave patterns and allows us to ‘see’ sound. © Boardworks Ltd 2004 2005
  7. 7. Loudness and amplitude A sound can be quiet or loud. quiet sound loud sound On an oscilloscope trace, the loudness of a sound is shown by the height of the wave. This is called the amplitude. Which word should be crossed out in this sentence? The larger the amplitude of the wave on the trace, the louder/quieter the sound. 1 of 36 20 7 © Boardworks Ltd 2004 2005
  8. 8. Which is the loudest? Which trace represents the loudest sound? A B Sound A is the loudest. Sound A has the largest amplitude (i.e. the tallest waves), so it is the loudest of these two sounds. 1 of 36 20 8 © Boardworks Ltd 2004 2005
  9. 9. Pitch and frequency A sound can be high or low – this is the pitch of the sound. low pitch sound high pitch sound On an oscilloscope trace, the pitch of a sound is shown by how many waves there are. This is called the frequency. Which word should be crossed out in this sentence? The greater the number of waves across the oscilloscope trace, the lower/higher the frequency and pitch. 1 of 36 20 9 © Boardworks Ltd 2004 2005
  10. 10. Which is the highest? Which trace represents the sound with the highest pitch? A B Sound B is the highest pitched. Sound B has the most number of waves across the oscilloscope – it has the highest frequency and so has the highest pitch. 1 of 20 10 of 36 © Boardworks Ltd 2004 2005
  11. 11. Wave animation 1 of 20 11 of 36 © Boardworks Ltd 2004 2005
  12. 12. Contents 8L Sound and Hearing What is sound? Speed of sound Reflecting sound The ear and hearing Summary activities 1 of 20 12 of 36 © Boardworks Ltd 2004 2005
  13. 13. Speed of sound experiment This investigation to calculate the speed of sound should be carried out in a quiet open space. START STOP 0 0 : 0 0 30 04 100 m 1. When you see the cymbals crash, press START. 2. When you hear the cymbals crash, press STOP. 1 of 20 13 of 36 © Boardworks Ltd 2004 2005
  14. 14. Speed of sound experiment – results table Record the results of the sound experiment. Experiment distance (m) 1 100 time (s) 0.34 speed (m/s) 294 2 3 4 How are these values used to estimate the speed of sound? distance 100 = = 294 m/s speed = time 0.34 1 of 20 14 of 36 © Boardworks Ltd 2004 2005
  15. 15. Speed of sound experiment – results The speed of sound in air is about… 340 m/s Use the results of the cymbals experiment to calculate the average speed of sound. How does this calculation for the average speed of sound compare with the real speed? What errors could have affected the results of the cymbals experiment? Do you think the speed of sound in water is the same as the speed of in air? 1 of 20 15 of 36 © Boardworks Ltd 2004 2005
  16. 16. Sound in different states of matter Sound needs a substance to travel through and travels by particles vibrating. Which state of matter does sound travel fastest through? solid liquid gas Sound waves travel fastest through solids. The particles in a solid are closer together than in a gas or a liquid. This means vibrations are more easily passed from particle to particle and so sound travels faster. 1 of 20 16 of 36 © Boardworks Ltd 2004 2005
  17. 17. Speed of sound in different materials Sound need particles to travel and the type of substance affects the speed of sound. 7000 6000 speed of sound (m/s) 6000 5000 5000 4000 3000 2000 1000 1450 330 350 air at 0 C air at 30 C 0 water concrete steel material 1 of 20 17 of 36 © Boardworks Ltd 2004 2005
  18. 18. Breaking the sound barrier! Which of these travel faster than the speed of sound in air? distance (m) time (s) speed (m/s) small aeroplane 600 5 120 jet fighter 900 2 450 cheetah 50 2.5 20 meteorite 10 000 0.35 28,571 The jet fighter and the meteorite travel faster than the speed of sound in air – this is called breaking the sound barrier. 1 of 20 18 of 36 © Boardworks Ltd 2004 2005
  19. 19. Sound or light – which is faster? During a thunderstorm, thunder and lightning are created at the same time. Which do you notice first? Usually, you see lightning before you hear thunder. Light travels much faster than sound. The speed of light is… 300,000,000 m/s How much faster is light than sound? How could you use thunder and the speed of sound to estimate how far away a thunderstorm is? 1 of 20 19 of 36 © Boardworks Ltd 2004 2005
  20. 20. Contents 8L Sound and Hearing What is sound? Speed of sound Reflecting sound The ear and hearing Summary activities 1 of 20 20 of 36 © Boardworks Ltd 2004 2005
  21. 21. Reflected sound What happens when a sound wave meets a hard flat surface? The sound wave is reflected back from the surface. This is called an echo. 1 of 20 21 of 36 © Boardworks Ltd 2004 2005
  22. 22. Echo experiment Stand at least 100 m from a large, flat wall with a stop watch. START 150 m STOP 1. Use a starting pistol (or clapper board) to make a sound. 2. Measure the time taken between firing the pistol and hearing the echo. 1 of 20 22 of 36 © Boardworks Ltd 2004 2005
  23. 23. Echo experiment The sound of the starting pistol takes 0.92 s to travel a distance of 300 m. How can you use this result to estimate the speed of sound? distance speed = time = 300 0.92 = 326 m/s Repeat the experiment several times to obtain an average. How does your calculation for the average speed of sound compare with the real value? 1 of 20 23 of 36 © Boardworks Ltd 2004 2005
  24. 24. Questions on reflecting sound 1. What is a reflected sound called? an echo 2. Are hard or soft surfaces best at reflecting sound? hard surfaces 3. Why are there soft materials on the walls of cinemas and theatres? to reduce echoes 4. Name two animals that use echoes for navigation or communication. bats and dolphins 1 of 20 24 of 36 © Boardworks Ltd 2004 2005
  25. 25. Contents 8L Sound and Hearing What is sound? Speed of sound Reflecting sound The ear and hearing Summary activities 1 of 20 25 of 36 © Boardworks Ltd 2004 2005
  26. 26. The ear and sound waves 1 of 20 26 of 36 © Boardworks Ltd 2004 2005
  27. 27. How does the ear hear? 1.Sound waves are collected by the ear lobe or pinna. 6.The auditory nerve takes the signals to the brain. 6 4 1 2 3 5 2.The waves travel along the ear canal. 5.The cochlea turns these into electrical 4.The small bones 3.The waves signals. (ossicles) amplify make the ear the vibrations. drum vibrate. 1 of 20 27 of 36 © Boardworks Ltd 2004 2005
  28. 28. Hearing range Set the volume and increase the frequency of the signal provided by the signal generator. Humans can only hear sounds of certain frequencies. The range of frequencies a person can hear is called their hearing range. What is the hearing range of a healthy young person? 20 Hz to 20,000 Hz 1 of 20 28 of 36 © Boardworks Ltd 2004 2005
  29. 29. Comparing hearing ranges Which animals hear the lowest and the highest frequencies? 100,000 10,000 1,000 frequency 100 (Hz) 10 1 0 human 1 of 20 29 of 36 dog bat elephant mouse dolphin © Boardworks Ltd 2004 2005
  30. 30. Hearing ranges and hearing loss Does everyone have the same hearing range? We all have slightly different hearing ranges People lose the ability to hear sounds of high frequency as they get older. Almost 1 in 5 people suffer some sort of hearing loss. Temporary hearing loss may be caused by ear infections and colds, after which hearing recovers. Permanent hearing loss and deafness can be present at birth or occur if the ear is damaged or diseased. 1 of 20 30 of 36 © Boardworks Ltd 2004 2005
  31. 31. Measuring loudness – the decibel scale decibels 160 aircraft overhead personal stereo 140 permanent ear damage 120 100 loud bell 80 quiet countryside 60 40 pin being dropped 1 of 20 31 of 36 20 0 circular saw at 2m can just be heard © Boardworks Ltd 2004 2005
  32. 32. Noise and its effects A noise is any unwanted sound. What one person considers noise another person might not. Can you name any examples? Noise can cause hearing problems. List three effects of noise. 1. headaches 2. nausea 3. deafness List three ways of reducing the effects of loud noise. 1. ear protectors 2. double glazing 3. putting noisy machinery in insulated rooms 1 of 20 32 of 36 © Boardworks Ltd 2004 2005
  33. 33. Contents 8L Sound and Hearing What is sound? Speed of sound Reflecting sound The ear and hearing Summary activities 1 of 20 33 of 36 © Boardworks Ltd 2004 2005
  34. 34. Glossary amplitude – The height of a wave, which shows how loud a sound is. cochlea – The part of the inner ear that changes vibrations into electrical signals which are then sent to the brain. decibel – The unit for measuring the loudness of sound (dB). eardrum – The thin membrane in the ear which vibrates when sound reaches it. frequency – The number of waves per second, which shows the pitch of a sound. hertz – The unit of frequency (Hz). 1 Hz = 1 wave per second. oscilloscope – An instrument that shows a picture of sound. pitch – How high or low a sound is. sound – A form of energy produced by vibrations, which is detected by the ears. 1 of 20 34 of 36 © Boardworks Ltd 2004 2005
  35. 35. Anagrams 1 of 20 35 of 36 © Boardworks Ltd 2004 2005
  36. 36. Multiple-choice quiz 1 of 20 36 of 36 © Boardworks Ltd 2004 2005

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