8Le - Noise Levels SLB

Noise Levels

8Le

Learning Objectives

• Recall that unpleasant sounds are called noise.• Recall that a decibel is a unit for the loudness of

sound.• Explain that soundproofing can be used to

reduce noise.• Recall how sounds are measured.• Explain the meaning of threshold of hearing.• Explain how soundproofing works

Annoyed by noise

• Sometimes sounds around you can be very annoying.

• Sound can damage your ears if its too loud or goes on for too long.

• Unpleasant sound is often called noise.

• We can measure how loud sound using a sound intensity meter in decibels (dB)

Guess the sound!!

• What is the sound?

• What decibel could it be?

150

140

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110

100

90

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0

VERYLOUD

QUIET

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Guess the sound!!150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

VERYLOUD

QUIET

1

2

3

4

5

6

7

8

1. Airplane2. Bird singing3. Drums4. Motorbike5. Bell6. Clock ticking7. Shouting8. Whispering/yawn9. City noise/traffic

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10 dB

20 dB

40 dB

50 dB

90 dB

100 dB

110 dB

120 dB

140 dB

Threshold of hearing• This is the quietest sound we can hear. • 0dB.

• The loudness of a road drill is 90dB.• This is the top limit accepted by law. • A noisy factory can be louder than this!• Dance speakers in a nightclub = 90dB.

• Sound becomes painful at 80dB!• Ear drums break at 180dB!!

FACT

• In November 1999, France brought out a law which limited the noise levels of personal stereos.

• Since 2000 no personal stereos can be played louder than 100dB.

Questions

1. What is the instrument which measures sound?

2. What units do we measure sound in?

3. What is the threshold of hearing?

4. What is the limit of acceptable noise?

5. Make a list of jobs which have a high level of noise.

Soundproofing• Houses near to an airport usually have

double glazed windows. Most of the air has been taken out from between the layers of glass.

• This makes it more difficult for sound to travel through – Why might this be?

• There are fewer particles to pass on vibrations.

Some people have to wear special ear protectors to stop their ears being damaged.

Noise can be reduced by soft things like curtains and carpets. The soft materials absorb some of the energy of

sound.

Practical – Soundproof designs

• Investigate which materials are the best for soundproofing.

• Choose the best way you think to collect and display the information.

• You will be given: bell, cardboard, paper, bubble wrap and other sound proofing materials.

Worksheet 8Le 2 or 3

Plenary – Zoo-reka!• The world renowned zoo and theme park ‘Zoo-

reka!’ has decided to employ people to help educate its visitors.

• You have been asked to lead tours and answer questions relating to the area of animals and sound.– How the enclosures keep the animals healthy and

clean.– How animals make sounds and what they use them

for.– How humans can listen to the sounds animals make.

•What would you say to Year 7’s about ‘Zoo-reka!’?

Level descriptors – ASP 336-337

Learning Objectives

• Recall that unpleasant sounds are called noise.• Recall that a decibel is a unit for the loudness of

sound.• Explain that soundproofing can be used to

reduce noise.• Recall how sounds are measured.• Explain the meaning of threshold of hearing.• Explain how soundproofing works