1. 09/11/2018
Think of as many things that make sound as you can, and for each of these think about what is vibrating.

2. Sound Waves Learning objectives:
09/11/2018
Sound Waves
Learning objectives:
Describe sound as a longitudinal wave.
Describe how the amplitude and frquency change the sound.

3. 09/11/2018

4. Q: What do mechanical waves need to move through?
09/11/2018
Q: What do mechanical waves need to move through?
Notes:
Mechanical waves need a medium to move through.
Sound waves move through the medium of air.
Sea waves move through the medium of water.

5. Q: What do mechanical waves need to move through?
09/11/2018
Q: What do mechanical waves need to move through?
Notes:
Mechanical waves need a medium to move through.
Sound waves move through the medium of air.
Sea waves move through the medium of water.

6. Q: What do mechanical waves need to move through?
09/11/2018
Q: What do mechanical waves need to move through?
Notes:
Mechanical waves need a medium to move through.
Sound waves move through the medium of air.
Sea waves move through the medium of water.
Level 7 Extension: what medium do light waves need to travel through?
Answer: none, they can travel through a vacuum. Light is massless meaning it is not made of matter. Light is just pure energy.
Level 7 Extension: what medium do light waves need to travel through?

7. How could astronauts talk in space without using a radio?
09/11/2018
How could astronauts talk in space without using a radio?

8. Demonstration 1 – salt grains on a loudspeaker.
09/11/2018
Demonstration 1 – salt grains on a loudspeaker.
Which directions to the salt grains move in? What does this tell you about the direction the speaker cone is moving in?
What direction do the sound waves move in?
What does this tell you about what type of waves sound waves are?
(hint: compare the direction of the vibrations and the direction the waves move in)
Skip to 1:40 on youtube clip.

9. Demonstration 2 – bell in a vacuum jar.
09/11/2018
Demonstration 2 – bell in a vacuum jar.
What happens to the sound of the bell when the air is pumped out of the vacuum jar?
What does this tell you about sound waves?

10. Bell jar animation 09/11/2018 Works in presentation mode
Click the valve and pump
Ensure speakers are on

11. 09/11/2018
Notes:
Sound waves are mechanical waves. This means that they need a medium (e.g., air) to travel through.
Sound waves are longitudinal waves. This is because the direction of the vibrations is parallel to the direction the wave travels.
mechanical
vibrations
parallel
longitudinal
medium

12. 09/11/2018
Notes:
Sound waves are mechanical waves. This means that they need a medium (e.g., air) to travel through.
Sound waves are longitudinal waves. This is because the direction of the vibrations is parallel to the direction the wave travels.

13. 09/11/2018
Notes:
Sound waves are mechanical waves. This means that they need a medium (e.g., air) to travel through.
Sound waves are longitudinal waves. This is because the direction of the vibrations is parallel to the direction the wave travels.

14. 09/11/2018
Notes:
Sound waves are mechanical waves. This means that they need a medium (e.g., air) to travel through.
Sound waves are longitudinal waves. This is because the direction of the vibrations is parallel to the direction the wave travels.

15. 09/11/2018
Notes:
Sound waves are mechanical waves. This means that they need a medium (e.g., air) to travel through.
Sound waves are longitudinal waves. This is because the direction of the vibrations is parallel to the direction the wave travels.

16. 09/11/2018
Notes:
Sound waves are mechanical waves. This means that they need a medium (e.g., air) to travel through.
Sound waves are longitudinal waves. This is because the direction of the vibrations is parallel to the direction the wave travels.

17. How do sound waves travel?
09/11/2018
How do sound waves travel?
Recording your results
Write the name of each material or object under the correct heading in the table.
Considering your results/conclusions
A vibrating object pushes air particles side to side.
These air particles bump into other air particles and then continue to move back and forth.
The particles in the air become compressed in compression zones and spread out in rarefaction zones.

18. Speed of sound
09/11/2018
Predict which material will have the fastest speed of sound.
Enter distance = 10000
Animation works in presentation mode

19. Task – complete w/s 8G L3. 09/11/2018 Solid Liquid Gas
The particles are very close together
How close together are the particles?
How often do they bump into each other?
How easy is it for the vibrations to be passed on?
Differentiation EXTENSION worksheet has extension task: Double glazing windows have low pressure air between two panes of glass. Explain how double glazing reduces the amount of sound energy that goes through the window.
Answer: First you can describe speed – fast in the glass, slower in the air in the gap. Low pressure air means fewer particles so the sound cannot travel well through the air. A lot of the sound is reflected off the first pane of glass and reflected again off the second pane of glass due to this large change in speed.
How fast does sound travel in this medium?

20. Task – complete w/s 8G L3. 09/11/2018 Solid Liquid Gas
The particles are very close together
The particles are close together
The particles are very far apart
How close together are the particles?
How often do they bump into each other?
How easy is it for the vibrations to be passed on?
How fast does sound travel in this medium?

21. Task – complete w/s 8G L3. 09/11/2018 Solid Liquid Gas
The particles are very close together
The particles are close together
The particles are very far apart
Particles often bump into each other
Particles bump into each other less often
Particles do not often bump into each other
How close together are the particles?
How often do they bump into each other?
How easy is it for the vibrations to be passed on?
How fast does sound travel in this medium?

22. Task – complete w/s 8G L3. 09/11/2018 Solid Liquid Gas
The particles are very close together
The particles are close together
The particles are very far apart
Particles often bump into each other
Particles bump into each other less often
Particles do not often bump into each other
It is easy for vibrations to be passed on
It is less easy for vibrations to be passed on
It is difficult for vibrations to be passed on
How close together are the particles?
How often do they bump into each other?
How easy is it for the vibrations to be passed on?
How fast does sound travel in this medium?

23. Task – complete w/s 8G L3. 09/11/2018 Solid Liquid Gas
The particles are very close together
The particles are close together
The particles are very far apart
Particles often bump into each other
Particles bump into each other less often
Particles do not often bump into each other
It is easy for vibrations to be passed on
It is less easy for vibrations to be passed on
It is difficult for vibrations to be passed on
Sound travels faster than in liquids and gases
Sound travels faster than in gases
Sound travels slowest in gases
How close together are the particles?
How often do they bump into each other?
How easy is it for the vibrations to be passed on?
How fast does sound travel in this medium?

24. 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

25. 09/11/2018
Put these in order of how fast sound travels through them – start with the fastest:
air space water rock

26. space (slowest – sound doesn’t travel through space at all)
09/11/2018
Put these in order of how fast sound travels through them – start with the fastest:
rock (fastest)
water
air
space (slowest – sound doesn’t travel through space at all)

27. How does the ear work?
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

28. The human ear can hear frequencies that range from 20 Hz to 20,000 Hz.
09/11/2018
The human ear can hear frequencies that range from 20 Hz to 20,000 Hz.

29. The human ear can hear frequencies that range from 20 Hz to 20,000 Hz.
09/11/2018
The human ear can hear frequencies that range from 20 Hz to 20,000 Hz.

30. 09/11/2018
How loud does a sound have to be before we can hear it? What happens if it is too loud?

31. The loudness of a sound is measured in decibels (dB).
09/11/2018
How loud does a sound have to be before we can hear it? What happens if it is too loud?
The loudness of a sound is measured in decibels (dB).
The quietest sound we can hear is 0 dB. This is called the threshold of hearing.
Sound starts to become painful at 134 dB.
The eardrum breaks at 185 dB.
(p 172)

32. The loudness of a sound is measured in decibels (dB).
09/11/2018
How loud does a sound have to be before we can hear it? What happens if it is too loud?
The loudness of a sound is measured in decibels (dB).
The quietest sound we can hear is 0 dB. This is called the threshold of hearing.
Sound starts to become painful at 134 dB.
The eardrum breaks at 185 dB.

33. The loudness of a sound is measured in decibels (dB).
09/11/2018
How loud does a sound have to be before we can hear it? What happens if it is too loud?
The loudness of a sound is measured in decibels (dB).
The quietest sound we can hear is 0 dB. This is called the threshold of hearing.
Sound starts to become painful at 134 dB.
The eardrum breaks at 185 dB.
(p 172)

34. The loudness of a sound is measured in decibels (dB).
09/11/2018
How loud does a sound have to be before we can hear it? What happens if it is too loud?
The loudness of a sound is measured in decibels (dB).
The quietest sound we can hear is 0 dB. This is called the threshold of hearing.
Sound starts to become painful at 134 dB.
The eardrum breaks at 185 dB.
(p 172)

35. The loudness of a sound is measured in decibels (dB).
09/11/2018
How loud does a sound have to be before we can hear it? What happens if it is too loud?
The loudness of a sound is measured in decibels (dB).
The quietest sound we can hear is 0 dB. This is called the threshold of hearing.
Sound starts to become painful at 134 dB.
The eardrum breaks at 185 dB.
(p 172)

36. The larger the amplitude, the louder the sound.
09/11/2018
Notes:
The amplitude (size of the vibrations) is half of the height of the wave and is measured in metres (m).
amplitude
amplitude
The larger the amplitude, the louder the sound.

37. 09/11/2018
Notes:
The distance between waves is the wavelength, measured in metres (m).
wavelength
The shorter the wavelength, the higher the frequency.
Short wavelength, high frequency.
Long wavelength, low frequency.

38. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
Low pitch
(low frequency)
High pitch
(high frequency)

39. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

40. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
Low frequency
(low pitch)

41. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

42. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
Low frequency
(low pitch)

43. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

44. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
High frequency
(high pitch)

45. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

46. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
High frequency
(high pitch)

47. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

48. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
Low frequency
(low pitch)

49. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

50. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
Low frequency
(low pitch)

51. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

52. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
High frequency
(high pitch)

53. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?

54. When the frequency of sound waves change, we hear different pitches.
09/11/2018
When the frequency of sound waves change, we hear different pitches.
What sort of pitch (frequency) sound would you expect from these animals and instruments?
Low frequency
(low pitch)

55. 09/11/2018
If different animals make different pitch sounds, do you think they can hear different pitch sounds?
Yep – some dog whistles can’t be heard by humans as they are ultrasonic

56. Interactive oscilloscope
09/11/2018

57. Compare the sounds for the following waves.
Plenary:
Compare the sounds for the following waves. A D B E
Same frequencies / wavlengths: D & F, A & E.
Same amplitudes: B & E, C & F C F