# NCERT Solutions for Class 8 Science Chapter 13 Sound

In this page you will find NCERT Solutions for Class 8 Science Chapter 13 Sound that are prepared by our experts try to provide all round clarity of questions. These are helpful in building a great foundation of concepts and make easy for the students to understand basics. It will improve your awareness skills sharply and you can easily memorize more things precisely.

NCERT Solutions for Class 8 Science is an effective method for learning since you can be le to learn a lot within a short time. Chapter 13 Sound Class 8 Science NCERT Questions and Answers will develop the ability to identify what improvements and changes need to be made. It is very challenging to score good marks in tests that is why we have prepared NCERT Solutions.

## NCERT Solutions for Class 8 Science Chapter 13 Sound

You can pinpoint your weaknesses with the help of these NCERT Solutions for Class 8 Science Chapter 13 and prepare accordingly to change it in a positive way. Detailed explanation provided under each NCERT solutions will help in understanding the concepts better. In the examinations, you will can come up with better answers and lay out the main point effectively.

Study Material for Class 8 Science Chapter 13 Sound

Page No: 168

Exercise

1. Choose the correct answer.
Sound can travel through
(a) gases only
(b) solids only
(c) liquids only
(d) solids, liquids and gases.
► (d) solids, liquids and gases.

2. Which of the following voices is likely to have minimum frequency?
(a) Baby girl
(b) Baby boy
(c) A man
(d) A woman
► (c) A man

Page No: 169

3. In the following statements, tick 'T' against those which are true, and 'F' against those which are false.

(a) Sound cannot travel in vacuum. (T / F)
► True

(b) The number of oscillations per second of a vibrating object is called its time period. (T / F)
► False

(c) If the amplitude of vibration is large, sound is feeble. (T / F)
► False

(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T / F)
► True

(e) The lower the frequency of vibration, the higher is the pitch. (T / F)
► False

(f) Unwanted or unpleasant sound is termed as music. (T / F)
► False

(g) Noise pollution may cause partial hearing impairment. (T/F)
► True

4. Fill in the blanks with suitable words.
(a) Time taken by an object to complete one oscillation is called _________.
(b) Loudness is determined by the________ of vibration.
(c) The unit of frequency is _________.
(d) Unwanted sound is called _________.
(e) Shrillness of a sound is determined by the _________of vibration.

(a) Time taken by an object to complete one oscillation is called time period.
(b) Loudness is determined by the amplitude of vibration.
(c) The unit of frequency is hertz (Hz).
(d) Unwanted sound is called noise.
(e) Shrillness of a sound is determined by the frequency of vibration.

5. A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.

Frequency of oscillations is the number of oscillations of a vibrating object per second. Therefore frequency is = 40 vibrations /4 seconds= 10 Hertz.
Time period is the time required to complete one oscillation. Or it is the inverse of time period. Therefore time period = 1/10 = 0.1 seconds.

6. The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?

Time Period given by the inverse of the frequency.
Time Period= 1/Frequency of oscillation = 1/500 = 0.002 sec.

7. Identify the part which vibrates to produce sound in the following instruments.
(a) Dholak (b) Sitar (c) Flute

(a) Diaphragm (stretched membrane)
(b) String
(c) Air column

8. What is the difference between noise and music? Can music become noise sometimes?

Unwanted sound that is unpleasant to ear is called noise. A pleasant sound is called music.
Music can become noise at many instances. When someone tries to enjoy very loud music, it can be noise for someone else. When loud music is played during religious celebrations or marriages, it can be annoying for many people.

9. List sources of noise pollution in your surroundings.

Some sources of noise pollution are as follows:
→ Televisions and transistors running at high volumes
→ Loudspeakers and crackers
→ Horns of buses, cars and trucks
→ Home appliances such as mixer, desert cooler, etc.

10. Explain in what way noise pollution is harmful to humans.

Noise pollution is harmful to humans in many ways. Constant exposure to noise pollution can create many health related problems; like insomnia, hypertension and may even lead to loss of hearing.

11. Your parents are going to buy a house. They have been offered one on the roadside and another three lanes away from the roadside. Which house would you suggest your parents should buy? Explain your answer.

There will be more noise in the house which is along the roadside due to noise produced by transportation vehicles may cause trouble to the residents. On the other hand, the house which is three lanes away from the roadside would be quieter. Therefore, it is better to take the house that is three lanes away from the roadside.

12. Sketch larynx and explain its function in your own words.

Larynx is a part of the throat. It is responsible for production of sound.

13. Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain?

The speed of sound is less than the speed of light. Due to this, light reaches to us faster than sound. Hence, during lightning we see the streak of light earlier than hearing the sound of thunder.

## Chapter 13 Sound Class 8 Science NCERT Solutions

Class 8 Science NCERT Solutions of Chapter 13 Sound help you in improving the marks in the examinations and have edge over your classmates. These NCERT Solutions are curated by the experts in a comprehensive which can be helpful in clearing your doubts instantly. Students should also refer previous year questions and practise test papers and worksheets to assess their key areas.

### Class 8 Science Chapter 12 Friction NCERT Questions and Answers - Topics

• Sound is Produced by a Vibrating Body
• Sound Produced by Humans
• Sound Needs a Medium for Propagation
• We Hear Sound through Our Ears
• Amplitude, Time Period and Frequency of a Vibration
→ Loudness and Pitch
• Audible and Inaudible Sounds
• Noise and Music
• Noise Pollution
→ What are the Harms of Noise Pollution?
→ Measures to Limit Noise Pollution

### Chapter 13 Sound NCERT Solutions for Class 8 Science  - Notes

• Sound is very important for our life. It is the sound that helps us to communicate with each other.

• The to and fro or back and forth motion of an object is called vibration.

• Musical instruments produce different types of sound because of vibration.

• In humans, the sound is produced by the voice box or the larynx. It is at the upper end of the windpipe. Two vocal cords, are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the passage of air. When air passes through those stretched membranes they produce different types of sound with different combinations of stretching.

• The traveling of sound is called propagation of sound. The place where there is no air or air is removed, is called vacuum. Sound does not propagate through vacuum. Sound travels through solid, liquid and gas.

• We hear sound through our ear. The shape of the outer part of the ear is like a funnel. When sound enters it, it travels down a canal at the end of which there is a thin stretched membrane. It is called the eardrum. The eardrum is like a stretched rubber sheet. Sound vibrations make the eardrum vibrate. The eardrum sends vibrations to the inner ear. From there, the signal goes to the brain and we hear.

• The to and fro motion of an object is known as vibration also called oscillatory motion.

• The number of oscillations per second is called the frequency of oscillation. Frequency is expressed in hertz. Its symbol is Hz.

• The loudness of sound depends on its amplitude. When the amplitude of vibration is large, the sound produced is loud.

• The frequency determines the shrillness or pitch of a sound. If the frequency of vibration is higher we say that the sound is shrill and has a higher pitch. If the frequency of vibration is lower, we say that the sound has a lower pitch.

• The sounds of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear. Such sounds are called inaudible. The sounds of frequencies higher than about 20,000 vibrations per second (20 kHz) are also not audible to the human ear.

• Sound that appears unpleasant to us is called noise. Musical sound is one which is pleasing to the ear.

• The presence of excessive or unwanted sounds in the environment is called noise pollution.

• The presence of excessive noise in the surroundings may cause many health related problems. Lack of sleep, hypertension (high blood- pressure), anxiety and many more health disorders may be caused by noise pollution.

• A person who is exposed to a loud sound continuously may get temporary or even permanent impairment of hearing.

• Measures to Limit Noise Pollution
→ Noise producing industries should be set up away from such areas.
→ Use of automobile horns should be minimised.
→ TV and music systems should be run at low volumes.
→ Trees must be planted along the roads and around buildings to cut down on the sounds reaching the residents.

### Chapter 13 Sound Class 8 Science Questions and Answers - MCQ Questions with answers

1. The pitch of sound depends on:
a) Frequency
b) Amplitude
c) Both of the above
d) None of the above
► a) Frequency

2. When a tightly stretched band is plucked, it
a) Only oscillate to and fro
b) Produce sound but do not vibrate
c) Vibrate but do not produce sound
d) Vibrate and produce sound
► d) Vibrate and produce sound

3. The nature of sound waves is
a) Longitudinal wave
b) Transverse wave
c) Electromagnetic wave
d) Mechanical wave
► a) Longitudinal wave

4. The hearing range of human ear is:
a) 20 Hz to 20,000 Hz.
b) Less than 20 Hz.
c) More than 20,000 Hz.
d) 20 Hz to 25,000 Hz.
► a) 20 Hz to 20,000 Hz.

5. Which of the following factor influence speed of sound most?
a) Humidity
b) Source of sound
c) Nature of medium
d) Temperature
► c) Nature of medium

6. Eardrum is a part of:
a) Sound producing organ
b) Skeletal system
c) Hearing organ
d) Reproductive organ
► c) Hearing organ

7. Damage to which of the following parts of ear cause hearing impairment?
a) Pinna
b) Oval window
c) Tympanic membrane
d) Ear canal
► c) Tympanic membrane

8. The voice box is also called:
a) Stomach
b) Heart
c) Larynx
d) Mouth
► c) Larynx

9. Tympanic membrane is another name of
a) Eardrum
b) Cochlea
c) Voice-box
d) Anvil
► a) Eardrum

10. Sound cannot travel through
a) Solids
b) Water
c) Vacuum
d) Air
► c) Vacuum

Given NCERT Solutions are available in understandable language in order to be effective and perform better in the class. It will develop logical perspective of students and they will be more scientific while answering a question. These Class 8 Science NCERT Solutions will be quite helpful in making learning process and effortless and more effective.

 NCERT Solutions for Chapter 1 Crop Production and Management NCERT Solutions for Chapter 2 Microorganisms Friend and Foe NCERT Solutions for Chapter 3 Synthetic Fibres and Plastics NCERT Solutions for Chapter 4 Metals and Non-Metals NCERT Solutions for Chapter 5 Coal and Petroleum NCERT Solutions for Chapter 6 Combustion and Flame NCERT Solutions for Chapter 7 Conservation of Plants and Animals NCERT Solutions for Chapter 8 Cell Structure and Functions NCERT Solutions for Chapter 9 Reproduction in Animals NCERT Solutions for Chapter 10 Reaching the Age of Adolescence NCERT Solutions for Chapter 11 Force and Pressure NCERT Solutions for Chapter 12 Friction NCERT Solutions for Chapter 14 Chemical Effects of Electric Current NCERT Solutions for Chapter 15 Some Natural Phenomena NCERT Solutions for Chapter 16 Light NCERT Solutions for Chapter 17 Stars and the Solar System NCERT Solutions for Chapter 18 Pollution of Air and Water