Ch.13: Sound

Sound | Class 6 | Science | Chapter 13 | Maharashtra State Board

In this fascinating video, we will be exploring the world of sound - what it is, how it is produced and how it travels through the air to reach our ears. We will delve into the science behind sound waves and explain the difference between sound and noise. Did you know that our voice box, located in our throat, plays a crucial role in producing sound? We will also discuss the various factors that affect the speed of sound and how it propagates from one medium to another. Additionally, we will touch upon the topic of noise pollution and its harmful effects on human health and the environment. By the end of this video, you will have a deeper understanding of the principles of sound and be equipped with practical tips on how to prevent noise pollution in your daily life.

Questions & Answers

1. Fill in the blanks using the proper words.

1. The propagation of sound does not occur through a vacuum.

2. Noise pollution is a social issue.

3. The sound which is disagreeable to the ears is called noise.

4. Noise has adverse effects on our Health/ mind/ concentration/ ears.

2. What should we do?

(a) The silencer of a motorcycle is broken.

Ans. The silencer should be repair immediately to reduce noise pollution. Driving such a motorcycle should not be attempted till the silencer is fixed.

(b) A factory in the surroundings is producing continuous loud noise.

Ans. We should inform about the loud noise to the authorities of the factories. If there is any problem with machinery in the factories, it should be repaired by the owners of the factory. If they are not paying any heed, then we can complain to the nearby police station.

3. Write the answers in your own words.

(a) What is meant by vibration?

Ans. The rapid oscillations or to and fro movements of an object is called vibration. Vibrating objects have a particular speed.

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

Ans. Sound propagates with a maximum speed through the solid medium. We can hear the sound of a train which is far off by placing our ear to the railway track. If we knock at the door, the person inside the room can hear it clearly.

(c) What is meant by noise pollution?

Ans. A condition in which there is continuous, unwanted and unpleasant sound is called noise pollution.

(d) What measures will you take to control noise pollution?

Ans. Five measures to reduce noise pollution are:

• Lower the volumes of the electrical appliances like TV, smartphones etc.

• Follow the limits of noise level.

• Shut the doors and windows while using the noisy machines.

• Use headphones or earphones while listening or music or watching videos on smartphones.

• Stay away from noisy area to prevent your ears from getting harm or being deaf.

3. Complete the table.

Nature of sound	Unpleasant	Pleasant
Speaking	Speaking in shouting and harsh tone	Soft speech
Whispering	​-	Yes
Aeroplane sounds	Yes	-
Horn of vehicles	Yes	-
Railway engine	Yes	-
Rustling of leaves	-	Yes
Neighing of a horse	Yes	-
Ticking of a clock	-	Yes

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E X T R A

1. Define the following.

(a) Vibration

Ans. The to and fro motion of an object about its mean position is called Vibration.

(b) Propagation of Sound

Ans. Sound waves spread in all directions from a source of sound. It is called Propagation of sound.

(c) Acoustics

Ans. The science of sound resonance (the quality of sound) including the production, propagation and effects of sound is called Acoustics.

(d) Medium

Ans. The substance or matter through which sound waves are propagated is called Medium.

2. Distinguish Between.

Music (Pleasant sound)	Noise (Unpleasant sound)
Music is pleasant to hear.	Noise produces an unpleasant effect in the surroundings.
It is produced by regular and periodic vibrations.	It is produced by irregular and non-periodic vibrations.
e.g. Sound produced by musical instruments like sitar, violin, etc.	e.g. Sounds produced by machines in a factory, sound produced in a crowded area.

3. Give Scientific Reasons.

(a) Silencers should be fitted in the engines of the automobiles.

Ans.

1. Noise pollution causes discomfort to human and animal life.

2. Silencers help to reduce the sound produced by the engines thus preventing noise pollution.

Hence, silencers should be fitted in the engines of the automobiles to control the level of the noise produced in the environment.

(b) Sound is heard most clearly through a solid medium.

Ans.

1. Sound is a form of energy.

2. Sound waves require a medium to travel.

3. Transmission of sound occurs at a different speed through different mediums (solid, liquid and gas) due to the vibration of particles in the substance.

4. As the particles in solids are packed very tightly, the particles transmit the vibrations faster than other mediums.

5. Sound travels fastest through solids.

Hence, sound is heard most clearly through a solid medium.

4. Answer the following.

(a) What is Noise Pollution?

Ans. The unwanted and unpleasant sound, that causes discomfort of any kind in the environment is called Noise Pollution. Noise pollution is caused due to industrial noise, increase in the number of vehicles, honking cars, increasing pollution, bursting of crackers, loud music played during festivals etc.

(b) What measures should we take to control noise pollution?

Ans. Measures to control noise pollution are:

1. Honking should be prohibited especially in the “Silence Zones” like schools, hospitals, residential buildings etc.

2. The volume of TV or radio should be kept at minimum, restricted to those watching the programs.

3. Machines should be maintained in good condition to reduce industrial noise pollution.

(c) Explain how is sound propagated and heard by us?

Ans.

1. Air is present all around us.

2. As the source emits sound waves, the layer of air nearest to the source also vibrates leading to the propagation of sound waves.

3. When the sound waves reach our ears, the eardrum starts vibrating.

4. The sensation produced by these vibrations are passed on to the brain through the auditory nerves and then we are able to hear the sound.

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