13: Sound

Q.1. Fill in the blanks with the proper words.

(a) The propagation of sound does not occur through a vacuum .

(b) Noise pollution is a social issue.

(c) The sound which is disagreeable to our ears is called noise .

(d) Noise has adverse effects on our health .

Q.2. What should we do?

(a) The silencer of a motorcycle is broken.
Ans:If the silencer of a motorcycle is broken so it should be taken to the garage for repair immediately.If silencer is not maintained properly, it will start making loud noise on the road when it is in motion,it leads to noise pollution.

(b) A factory in the surrounding is producing continuous loud noise.
Ans: Factories should be located at a proper distance away from residential areas. Authorities should be contacted who will control the decibel level.

Q.3. Write the answers in your own words.

(a) What is meant by vibration?
Ans: The vibration of an object is necessary for the production of sound. As long as the object vibrates, the sound is heard. When the vibration stops, the sound also stops.

(b) Explain with the help of practical examples how sound is propagated through solids.

Ans: 1. Singing

2. Chirping of birds
3. Bursting of crackers
4. Whispering
5. Whistling
6. Flute
7. Honking
8. Dog barking

(c) What is meant by noise pollution?
Ans: The continuous noise which has ill effects is called noise pollution.

(d) What measures will you take to control noise pollution?
Ans: Measures for preventing noise pollution:

1. As far as possible, we should avoid blowing the horn.
2. The volume of the TV or radio in the house should be restricted to those watching the programmes.
3. Vehicle should be maintained properly to reduce the unnecessary sounds they produce.
4. Factories, airports, railway stations and bus stands should be located at the proper distance, away from residential area.

Q.4. Complete the table.