UNIT NO.6b
Sound
(Solved Exercise)
Choose the correct answer.
i. The volume of sound is measured in
a. noise
b. frequency
c. decibels
d. hertz
ii. Which of the following sounds might cause us pain?
a. a jet engine far away
b. birdsong
c. a jet engine close by
d. whispering
iii. The particles of which of the following materials are closest to each other?
a. water
b. brick
c. air
d. juice
iv. Sound waves cannot travel through
a. solids
b. liquids
c. gases
d. a vacuum
v. The thin piece of material in a microphone is called a
a. diaphragm
b. diagram
c. speaker
d. amplifier
3. Fill in the blanks.
i. Sound waves need a medium to travel through; they cannot travel through empty space.
ii. The volume of a sound is measured in decibel.
iii. The number of vibrations per second is called Frequency.
iv. The number of vibrations is measured in units called Hertz.
v. Sounds of over 85 decibels can cause us pain.
vi. Sound travels most slowly through a gas medium.
vii. Sound travels fastest through a solid medium.
Answer the following.
i. Define the following terms.
a. sound b. noise pollution
Answer:
Sound
Sound is a form of energy produced by vibrations. Sound travels in waves.
Noise Pollution
Noise pollution is the presence of unwanted, excessive or harmful sound in the environment.
ii. Explain in your own words what the difference is between music and noise.
Answer:
| Music | Noise |
| 1. Music is the sound that is pleasant and has a regular pattern of vibrations. | 1. Noise is the sound that is upleasant, irregular and unwanted. |
| 2. Music makes you feel happy. | 2. Noise can cause headache and stress. |
| 3. Music has a clear pitch and rhythm. | 3. Noise has no clear pitch or rhythm. |
iii. Name three kinds of noise pollution and ways to reduce them?
Answer:
1- Traffic Noise
Cars, buses, motercycles, trains are the cause of noise pollution. To reduce it we should use public transport and electric whicles.
2. Industrial Noise
Factories, heavy machinery, generators etc are the cause of this noise pollution. To reduse it worker should wear ear protection and factories should be located away from residential areas.
3- Social Noise
Loud speakers, parties, markets, high volume music etc are the cause of this noise pollution. To reduce it use carpets, curtains, double gauged windows at home and use community guidelines for events.
iv. Explain why sound cannot travel in a vacuum.
Answer:
A vacuum is a space with no matter (solid, liquid and gas). Sound need a material medium to travel. That is why sound is silent in vacuum and cannot travel there.