Sound Class 8 Important Questions and Answers

Important questions of Class 8 Science Chapter 13 Sound is given below. These important questions will help students while preparing for the exam.  Practising these important questions will analyse their performance and work on their weak points. Score well in exam of Class 8 Science by going through these important questions. Students of Class 8 can download important questions of Class 8 Science Chapter 13 Sound PDF by clicking the link provided below.

Important Questions of Class 8 Science Chapter 13 Sound

Here you can get Class 8 Important Questions Science based on NCERT Text book for Class 8. Science Class 8 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Sound for Class 8 Science subject.

Very Short Answer Questions

1. What is sound?
Answer:
 Sound is the medium by which we communicate with one another.

2. How is sound produced?
Answer:
 Sound is produced by vibrating bodies.

3. Do all bodies can produce sound?
Answer:
 No, all bodies cannot produce sound.

4. What do you feel when you touch a sound producing school bell?
Answer: 
We feel the vibrations in the bell.

5. Touch the bell when it stops producing sound. Can you feel the vibrations?
Answer:
 No, we cannot feel vibrations.

6. What do you understand by this?
Answer:
 We understand that only vibrating bodies can produce sound.

7. What do you understand by vibrations?
Answer:
 The back and forth motion of an object is called vibration.

8. In some cases we cannot see vibrations explain why is it so?
Answer:
 When amplitude of vibrations is very small, then we cannot see them.

9. What is amplitude?
Answer: 
The maximum displacement of a vibrating body on one side is called amplitude.

10. Name a musical instrument which produces sound by air column.
Answer:
 Flute.

11. Name the sound producing organ in human.
Answer:
 Larynx.

12. What is the other name of larynx?
Answer:
 Larynx is also called voice box.

13. What are vocal cords?
Answer:
 The cords stretched across the voice box or larynx are called vocal cords.

14. Do all animals produce sound by vocal cords?
Answer:
 No, all animals do not produce sound by vocal cords.

15. On which quality of sound or voice depend?
Answer:
 The quality of sound or voice depends on the looseness or tightness of vocal cords.

16. Do the length of vocal cords is same in men and women?
Answer: 
No, the length of vocal cords is not same in men and women.

17. What is the length of vocal cords in men and women?
Answer:
 The length of vocal cords in men and women is 20 mm and 15 mm respectively.

18. How does sound travel from one place to another?
Answer:
 Sound travels through a material medium from one place to another.

19. Can sound travel through vacuum?
Answer:
 No, sound cannot travel through vacuum.

20. What types of medium is required to travel sound?
Answer: 
The medium may be solid, liquid or gas.

21. How do whales and dolphins hear the sound?
Answer:
 Whales and dolphins live in water. They hear sound through water.

22. Name the organs in human which receives sound.
Answer:
 Ears.

23. What is outer part of ear called?
Answer:
 The outer part of the ear is called pinna. It is funnel shaped.

24. What is eardrum?
Answer: 
A thin and stretched membrane is called eardrum.

25. What is oscillatory motion?
Answer:
 The vibratory motion is also called oscillatory motion.

26. What do you mean by frequency?
Answer: 
The number of oscillations in one second is called frequency.

27. Write the unit of frequency.
Answer:
 The unit of frequency is hertz.

28. Define hertz.
Answer:
 A frequency of one hertz is one oscillation per second.

29. What are the two main properties of a sound which help us to recognise sound?
Answer:
 Amplitude and frequency are the two important properties of sound.

30. Define time period.
Answer:
 The time taken by a vibrating body to complete one oscillation is called time period.

31. On which factor loudness of sound depend?
Answer:
 The loudness of sound depends on the amplitude.

32. What is pitch or shrillness of a sound?
Answer:
 The characteristics of sound which depends on its frequency is called pitch of a sound.

33. What is the hearing range of human ears?
Answer: 
Hearing range of human ears is 20 Hz to 20,000 Hz.

34. What are frequencies of sound which are inaudible?
Answer: 
Less than 20 Hz and more than 20,000 Hz are inaudible.

35. How does the amplitude affect the loudness of voice?
Answer:
 Higher is the amplitude, louder is the voice.

36. Why the sound of a baby is feeble?
Answer: 
The sound of a baby is feeble due to its small amplitude.

37. What frequencies are heard by dogs and cats?
Answer:
 The dogs can hear up to 40,000 Hz frequencies while cats can hear up to 70,000 Hz frequencies.

38. What is ultrasound?
Answer:
 The sound having frequency more than 20,000 Hz is called ultrasound.

39. What is noise?
Answer:
 The loud sound which produces unpleasant sensation is called noise.

40. What do you mean by musical sound?
Answer:
 The sound which produces pleasant sensation is called musical sound.

41. Give examples of noise and musical sound.
Answer:
 The sound in classroom is noise while sound of any musical instrument is musical sound.

42. What do you mean by air pollution?
Answer:
 Presence of unwanted gases and dust particles in air is called air pollution.

43. What is noise pollution?
Answer: 
Presence of excessive or unwanted sounds in environment is called noise pollution.

44. What sources in home may lead to noise?
Answer:
 Television, transistor, radio at high volume, desert coolers and air conditioners are the sources producing noise at home.

45. What is the unit of loudness?
Answer:
Decibel (dB).

46. What is the loudness of a normal conversation?
Answer:
 60 dB. 

47. Write a common ill effect of noise pollution.
Answer: 
The most common ill effect of noise pollution is temporary deafness.

48. Write any one method to control noise pollution.
Answer:
 To grow more and more plants along the road sides.

Short Answer Type Questions

1: Discuss the importance of sound in our life.

Answer: Sound plays an important role in our life; Sound helps us to communicate with one another. Sound is so important because animals are able to hear events all around them, no matter where their attention is focused or not.

2: How is sound produced?

Answer: Sound is produced by the vibrations of a body and is transmitted through material media in pressure waves made up of alternate condensations (forcing of the molecules of the medium together) and rarefactions (pulling of the molecules of the medium away from one another).

3: How does sound travel from one place to another?

Answer: Sound travels through a medium solid, liquid and gas. It cannot travel through vacuum.

4: Why some sounds are louder than others?

Answer: The loudness of sound depends upon its amplitude. , larger the amplitude of vibration the louder is the sound and vice versa.

5: Explain with an activity that vibrating object produces sound.

Answer: Take metal dish pour water into it, strike its edge with a spoon, you will hear a sound, now again strike the edge of dish and look at the surface of water inside it, you will observe that vibrating dish producing sound along with wave in water. This shows that there is vibration in dish which is producing sound.

6: Vibrating objects produces sound; can we see the vibrations all the time?

Answer: No, we cannot see the vibrations all the time as their amplitude is so small that we cannot see them rather we can feel them.

7: What are vibrating parts of Veena and Tabla?

Answer: Vibrating part of Veena that produces sound is stretched string and Vibrating part of Tabla that produces sound is stretched membrane.

8: What are vibrating parts of Flute? 

Answer: Vibrating part of Flute that produces sound is air column.

9: Name some musical instrument which are simply beaten or struck to produce melodious music.

Answer: Manjira, ghatam, not and kartal are some of the instruments that which are simply beaten or struck to produce melodious music.

10: How sound is produced from a guitar?

Answer: The string of the sitar is plucked it vibrate to produce sound, along with string other parts infact the whole instrument is forced to vibrate, and it is the sound of the vibration of the instrument that we hear.

11: Does any part of human body vibrate while speaking or singing a song?

Answer: Yes, while speaking or singing our voice box or larynx which is located at the upper end of the wind pipe vibrates.

12: Why the larynx in human body does vibrate while speaking or singing a song?

Answer: There are two vocal cords which 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 the lungs force air through the slit, the vocal cords vibrate producing sound.

13: Explain via an activity that sound travels in liquids.

Answer: Fill a bucket with water and shake a bell under the water with one hand make sure that the bell should not touch the body of the bucket. Now place your ear gently on the water surface, you will hear the sound of the ringing bell, thus we can say that sound can travel through water.

14: Explain via an activity that sound travels in solids.

Answer: Take a metal rod and hold its one end to your ear, ask your friend to tap at the other end of metal rod you will hear the sound of tapping, thus this proves that sound can travels through solid.

15: How water animals communicate in water?

Answer: Sound can travel through liquid. Fill a bucket with water and shake a bell under the water with one hand make sure that the bell should not touch the body of the bucket. Now place your ear gently on the water surface, you will hear the sound of the ringing bell, thus we can say that sound can travel through water.

16: Explain the function of eardrum in human beings.

Answer: The eardrum, or tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear in humans, it is like a stretched rubber sheet, sound vibrations make the eardrum vibrate. The ear drum sends vibration to the inner ear and from there signal is send to the brain and in this way we are able to hear the sounds around us.

17: What is eardrum?

Answer: The eardrum, or tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear in humans, it is like a stretched rubber sheet, sound vibrations make the eardrum vibrate. The ear drum sends vibration to the inner ear and from there signal is send to the brain and in this way we are able to hear the sounds around us.

18: Explain the functioning of human ear.

Answer: The eardrum, or tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear in humans, it is like a stretched rubber sheet, sound vibrations make the eardrum vibrate. The ear drum sends vibration to the inner ear and from there signal is send to the brain and in this way we are able to hear the sounds around us.

19: Why are sound waves called mechanical waves?

Answer: Sound waves force the medium particles to vibrate, because of the interaction of the particles present in that medium.

20: Why there is difference in sound of a baby and an adult?

Answer: The loudness of sound depends upon the amplitude of vibration, when the amplitude of vibration is large sound produced is large and when amplitude of vibration, is low sound produced is feeble. A baby has low amplitude of vibration in their ear drum thus sound produced by baby is low in compare to adults.

21: Name the factor which determines shrillness or pitch of a sound?

Answer: If the frequency of vibration is higher the sound has high pitch and if the frequency of vibration is lower the sound has low pitch.

22: Which of the two a drum or a whistle will produce sound with higher pitch and why?

Answer: Whistle will produce sound with higher pitch. If the frequency of vibration is higher the sound has high pitch and if the frequency of vibration is lower the sound has low pitch.

23: Which of the two a man or a woman will produce sound with higher pitch and why?

Answer: Woman will produce sound with higher pitch.If the frequency of vibration is higher the sound has high pitch and if the frequency of vibration is lower the sound has low pitch.

24: Differentiate between audible and in audible sounds.

Answer: Range of sound between frequencies 20 to 20,000 Hz is called audible sound as sound between these frequencies is easily audible to human beings. But range of sound less than 20 Hz and more than 20,000 Hz is called in audible sound as sound below 20 Hz and more than 20,000 Hz is not audible to human beings.

25: Is there any animal that can hear sound of frequencies higher than 20000 Hz?

Answer: Yes, dog can hear sounds of frequencies higher than 20000Hz, because of this ability of dog it is being used by police for investigation purposes.

26: Name some equipment that works at frequencies higher than 20000 Hz.

Answer: The ultra sound equipment used for tracking and investigating many medical problems works at frequencies higher than 20000 Hz.

27: Define noise along with examples.

Answer: Unpleasant and undesirable sounds are called noise. Example sound produced by horns of vehicles, sound coming from construction sites, sound produced by factories machineries etc.

28: Explain noise pollution and its causes.

Answer: Presence of excessive or unwanted sounds in the environment is called noise pollution, the main causes of noise pollution is the sound made by horns of vehicles, sound coming from construction sites, sound produced by factories machineries etc. in our home sound produced by television, transistor radio at high volume, air conditioner, coolers, some kitchen appliances like pressure cooker etc. contributes to noise pollution.

29: Your friend’s parents are going to buy a house; they have been offered one nearby a factory and another 50 km away from the factory in a less crowdie place. Which house you would suggest your friend’s parents should buy, and why?

Answer: The house that is 50 km away from the factory in a less crowdie place , because house near by the factory will have to face noise pollution because of the industrial machines and also there will be problem of air pollution there.

30: How noise pollution is harmful to human beings?

Answer: Noise pollution can lead to number of health related problems like

  • Hearing loss
  • Loss of sleep
  • Hypertension
  • Severe headache
  • Stress

31: What is the difference between noise and music, can music become noise sometimes?

Answer: The sound that is pleasing to the ear is called music like sound produced by guitar, piano etc. The sound that is unpleasing to the ear is called noise like sound produced by factories machineries, transport vehicles etc. Yes music can become noise if it is played at high volumes.

32: Define:
a. Reverberation of sound
b. Echo

Answer: The persistence of sound due to repeated reflection and its gradual fading away is known as reverberation of sound.

Echo: Echo is defined as a repetition of sound due to the reflection of original sound by a large and hard obstacle.

33: What is the intensity of sound?

Answer: The amount of sound energy passing each second through unit area is called the intensity of sound.

34: How is sound produced?

Answer: The vibrating bodies produce the sound. When a body vibrates, sound is produced. If vibrations are stopped the sound is not produced any more.

35: Explain the importance of sound in our daily life.

Answer: Sound play an important role in our daily life. Our life depends on sound for each and every action. Without sound we cannot know what others communicate or want to say. Sound enables us to communicate with each other.

35: What are musical instruments? How do they produce sound?

Answer: The devices which produce various types of sounds which are pleasant to our ears are called musical instruments. Such sound is called music. The musical instruments have strings or the stretched membranes attached or fixed to them. Some instruments have air columns. When these instruments vibrate, the sound is produced.

36: Explain with the help of an activity that vibrating bodies produce sound.

Answer: Take a rubber band, put it around the longer side of a pencil box. Insert two pencils between the box and stretched rubber. Pluck the rubber band somewhere in the middle. You hear a sound and also see that rubber band vibrates. This activity shows that vibrating objects produce sound.

37: Do you see the vibrations in all the cases?

Answer: The vibrating objects produce sound. In some cases the vibrations are easily visible to us. But in most of the cases, the vibrations are not visible due to very small amplitude. But the vibrations in all the cases can be felt.

38: What is ektara? Identify its vibrating part.

Answer: Take a hollow coconut shell or an earthen pot and make a musical instrument. Such instrument is called ektara. Play this instrument, you hear a sound. The stretched rubber band or a wire is its vibrating part.

Class 8 Science Chapter 13 Sound Important Question 1

39: Explain the principle on which Jaltrang works.

Answer: Jaltrang works on the principle that the quality of sound is changed as its frequency changes. Metal tumbler filled with water up to different heights, give vibrations of different frequencies, hence produce different types of sounds.

Class 8 Science Chapter 13 Sound Important Question 2

40: Name the organ in human that produces sound. How does it work?

Answer: In humans, the sound is produced by the voice box or larynx. The voice box has two vocal cords stretched across it, in such a way that it leaves a slit for the passage of air. When the lungs force air through slit, the vocal cords vibrate to produce sound.

41: Prove that sound needs a medium for propagation.

Answer: Take a metal glass tumbler. Place a cellphone in it. Ask your friend to give ring on this cellphone. Listen to the ring carefully. Now surround the rim of the tumbler with your hands. Put your mouth on opening between your hands. Indicate to your friend to give a ring again. Listen the ring while sucking air from the tumbler. The sound become very less. This activity shows that sound requires a medium to propagate.

42: What do you mean by vacuum? What happens to the loudness of sound in vacuum?

Answer: The decreasing amount of air causes decrease in the loudness of sound. When air is removed completely from a vessel, it is said that there is a vacuum. If all the air is sucked from the vessel, the sound would stop completely. The sound cannot travel through a vacuum.

43: Prove that sound can travel through the liquids.

Answer: Take a bucket, fill it with clean water. Take a small bell in one hand. Shake the bell inside the water to produce sound. Place your ear gently on the water surface. You can hear the sound. It indicates that sound can travel through liquids.

44: Prove that sound can travel through solids also.

Answer: Take a long metal rod or a metre scale and hold its one end to your ear. Ask your friend to gently scratch or tap at the other end of the metal rod. You can hear the sound. The sound reaches your ear through the solid rod. The other friends cannot hear the sound because sound is very low. This activity shows that sound travels in solids also.

Class 8 Science Chapter 13 Sound Important Question 3

45: How do human being hear the sounds?

Answer: The hearing organs in humans are ears. Ears have a stretched structure called eardrum. When ears receive sound, it enters down the ear canal and reach eardrum. Vibrations of sound vibrate the eardrum and it sends vibrations to inner ear from which vibrations are sent to brain for interpretation of sound.

46: What do you mean by an oscillatory motion?

Answer: The to and fro motion of the object is called vibration. This motion in either side of the object from its mean position is also called the oscillatory motion.

47: What is frequency? How does it affect the quality of sound?

Answer: The number of oscillations per second is called frequency. Its unit is hertz. A frequency of 1 Hz is one oscillation per second. The frequency determines the shrillness of sound. It is also called pitch of sound. The high frequency makes the pitch high and if the pitch is low, the frequency is less.

48: What are the two important properties of sound?

Answer: 
(i) Amplitude: It is the maximum displacement from the mean position of an oscillatory body. It controls the loudness of a sound. More the amplitude, more loud the sound is.
(ii) Frequency: The Number of oscillations in one second is called frequency. It controls the pitch of the sounds. High pitched sound means high frequency. The unit of frequency is hertz.

49: What do you mean by noise and musical sound?

 Answer: Noise: The unpleasant sounds are called noise. It is unwanted sound. It is harmful to our ears. 
Musical sound: 
The sound which produces pleasant sensations is called musical sound. It is produced by various musical instruments.

50: What is noise pollution?

Answer: Presence of unwanted and excessive sounds in the environment is called noise pollution. It causes discomfort to us. Excessive sounds are produced by honking of horns, loudspeakers, crackers and machines.

51: How can noise pollution be controlled?

Answer: The noise pollution can be controlled by reducing their sources. The blowing of horns should be avoided in residential areas, near schools or hospitals. The use of loudspeakers should also be avoided. TV and radio should be played at low volumes. Trees should be planted. Trees absorb excessive sounds on the roads.

Long Answer Type Questions

1: Explain the mechanism of hearing in human body.

Answer: Sound plays an important role in our life; Sound helps us to communicate with one another. Sound is so important because animals are able to hear events all around them, no matter where their attention is focused or not. The eardrum, or tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear in humans, it is like a stretched rubber sheet, sound vibrations make the eardrum vibrate. The ear drum sends vibration to the inner ear and from there signal is send to the brain and in this way we are able to hear the sounds around us.

2: “Sound travels through a medium, it cannot travel in vacuum”. Justify the statement.

Answer: Sound travels through a medium solid, liquid and gas. It cannot travel through vacuum. Fill a bucket with water and shake a bell under the water with one hand make sure that the bell should not touch the body of the bucket. Now place your ear gently on the water surface, you will hear the sound of the ringing bell, thus we can say that sound can travel through water. Take a metal rod and hold its one end to your ear, ask your friend to tap at the other end of metal rod you will hear the sound of tapping, thus this proves that sound can travels through solid.

3: A pendulum oscillates 50 times in 6 seconds. Find its time period and frequency.

Answer: Frequency of oscillation is defined as the number of oscillation of a vibrating body per second. it is given by

Frequency = no of oscillation/ time period
= 50/6
= 8.33 Hz

Time period =1/frequency of oscillation
= 1/ 8.33
= 0.12 seconds.

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