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## Online Education for Class 8 Science Chapter 13 Extra Questions and Answers Sound

Sound Class 8 Questions And Answers Pdf Question 1.
Name some of the musical instruments which are simply beaten or struck to produce music.
Such instruments are manjira, ghatam, kartal, dholak, etc.

Numericals On Sound Class 8 Icse Question 2.
What part in humans produces sound?
It is voice box in humans, that produces sound.

Icse Class 8 Physics Sound Questions And Answers Question 3.
Can sound travel through solid also?
Yes, the sound can travel through solids also.

Questions On Sound Class 8 Icse Question 4.
What is to and fro motion of an object called?
The to and fro motion of an object is called vibration or oscillatory motion.

Sound Question Answer Class 8 Question 7.
How is frequency of oscillation expressed?
The frequency of oscillation is expressed in terms of hertz. Its symbol is Hz. A frequency of one Hz is one oscillation per second.

Sound Class 8 Worksheet Icse Question 8.
If an object oscillates 20 times in one second, what would be its frequency?
As the frequency is the number of vibrations per second; so in this case, when, an object oscillates 20 times in one second, its frequency would be 20 Hz.

Sound Chapter Class 8 Pdf Questions And Answers Question 9.
Can we differentiate sounds on the basis of their amplitudes and frequencies?
Yes, with the help of amplitude and frequency we can differentiate two sounds easily.

Sound Lesson Class 8 Questions And Answers Question 10.
Define amplitude. How is it expressed?
The displacement of the oscillating body is the measure of the amplitude of vibration of the body. It is expressed in terms of metre (m).

Class 8 Sound Question Answer Question 11.
How is loudness of a sound determined?
The loudness of a sound is determined by its amplitude. When the amplitude of a vibration is large, the sound produced is loud, and in case of the smaller amplitude, the sound produced is feeble.

Sound Class 8 Icse Questions Question 12.
What is noise? Do you enjoy the sound produced by horns of buses and trucks? Why?
The unpleasant sounds are called noise. We do not enjoy the sounds produced by the horns of buses and trucks because these sounds are loud and harsh and hence are unpleasant sounds.

Question Answer Of Sound Class 8 Question 13.
What are the causes of hearing impairment?
Hearing impairment is generally the result of an ear disease, injury or degeneration of the hearing mechanism with age. The noise pollution also contributes to deafness.

Sound Class 8 Question Answer Question 14.
How can one improve hearing impairment? Is society and technology to contribute towards improving this defect?
Technological devices for the hearing impaired have made it possible for such persons to improve their quality of hearing. Society too can do much to improve the living environment for the hearing impaired by minimising noise pollution.

Sound Chapter Class 8 Of Icse Board Question 15.
What should be done to control noise pollution?
To control noise pollution, we must control the sources of noise at home or in the surroundings. We should also plant trees in the surroundings.

Question 16.
What is noise pollution and what are the harms due to it? Mention any two methods to limit noise pollution.
Noise pollution: Presence of excessive or unwanted sounds in the environment is called noise pollution.
Major causes of noise pollution are sounds of vehicles, explosions including bursting of crackers, machines, loudspeakers, etc.
Harms of noise pollution :
(a) The presence of excessive noise in the surroundings causes many health-related problems like lack of sleep, hypertension, anxiety, etc.

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

Methods to control noise pollution :

• Use of automobile horns should be minimised.
• TV and music systems should be run at low volumes.

Question 17.
What are audible and inaudible sounds? Describe.
Audible sounds: Sounds of frequencies between 20 to 20,000 hertz.
Inaudible sounds :

• Sounds of frequencies less than 20 hertz. Such sounds are called infrasonic.
• Sounds of frequencies more than 20,000 hertz. Such sounds are called ultrasonic.

Question 18.
What are the uses of ultrasound?
Uses of ultrasound :

• The ultrasound or ultrasonic sound is used in investigating and tracking many medical problems.
• In industries, ultrasound is used for detecting flaws and cracks in metallic and other structures.
• Some operations, like bloodless surgery, can be done by applying this sound.

Question 19.
Write a short note on the children having impaired hearing.
A child who has a moderately severe hearing loss and does not use a hearing aid will hear very little conversational speech because speech develops as the direct result of hearing. A child with a moderately severe hearing loss may have defective speech, minimal expressive vocabulary and inadequate language structure. So, children with impaired hearing need special care. By learning sign language such children can communicate effectively.

Question 20.
Describe the construction and working of ears with diagram.
We hear sound through our ears. The shape of the outer part of ear is like a funnel. When sound enters in it, it travels down a canal at the end of which a thin membrane is stretched tightly. It is called the eardrum.

Sound vibrations make the eardrums vibrate. The eardrum sends vibrations to the inner ear. From there, the signals go to the brain and we hear.

Question 21.
(a) Name the soundbox in human beings. Explain, how it works?
(b) A body vibrates 100 times in 20 seconds. Calculate the time period and frequency.
(a) The name of the voice box is larynx. The larynx or voice box is responsible for producing sounds in humans. The voice box consists of two vocal cords. These chords are arranged in such a manner that there is a small gap between them. This small gap allows air to pass through. When we speak, air is forced into this small gap by the lungs. The vibrations in the vocal cords produce the sound.

(b) Number of vibrations = 100
Time taken = 20 s
Time taken to complete one vibration 20
= $$\frac{20}{100}$$ sec =$$\frac{1}{5}$$ sec = 0.2 sec
Frequency = = 5Hz.

Multiple Choice Questions (MCQs)

1. The to and fro or back and forth motion of an object is termed as
(a) Simulation
(b) Allocation
(c) Vibration
(d) Elongation.
(c) Vibration.

2. Take a shallow frying pan. Hang it at a convenient place in such a way that it does not touch any wall. What will you feel if you strike the bottom of the pan with a stick and touch the pan gently with a finger?
(a) The bottom of the pan feels hot.
(b) The bottom of the pan feels cold.
(c) We can feel the smoothness of the surface.
(d) We can feel the vibrations.