# NCERT Class 8 Science Chapter 13 Sound Extra Questions

## NCERT Class 8 Science Chapter 13 Sound Extra Questions and Answers

Class 8 Science Chapter 13 Extra Questions and Answers – Sound. Here in this Page Class VIII Students can Learn Extra Questions & Answer 13th Chapter Science fully Inside.

We Provided Here Sound Science Chapter 13 Long Answer Type Question, Very Short Type Questions (VSA) / MCQ Type Questions, Short Type Questions (SA). 1) Fill in the blanks:

a) ____ is produced by vibrating objects. (Sound)

b) The unit of loudness is ____. (Decibel)

c) The vocal cords in men are about _____ mm long. (20)

d) _____ sends vibrations to the inner ear. (Eardrum)

2) Multiple choice questions:

a) The ultrasound equipment works at frequencies _____ than 20,000 Hz?

a) Higher b) Lower

Ans. a) Higher

b) A lion makes a _____ roar?

a) High-pitched b) Low-pitched

Ans. b) Low-pitched

c) A drum vibrates with a ____ frequency?

a) Low b) High

Ans. a) Low

d) The vocal cords in women are about _____ mm long?

a) 20 b) 15

Ans. b) 15

a) What is frequency? What is the unit of frequency?

Ans. The number of oscillations per second is called the frequency of oscillation.

The unit of frequency is Hertz.

b) How does the loudness of sound depend on its amplitude?

Ans. When the amplitude of vibration is large, the sound produced is loud. On the other hand, When the amplitude of vibration is small, the sound produced is feeble.

c) How does the frequency determine the pitch of a sound?

Ans. If the frequency of vibration is higher, the sound is shrill and has a higher pitch. On the other hand, if the frequency of vibration is lower, the sound has a lower pitch.

d) What is noise? What is the cause of noise pollution? State two effects of noise pollution.

Ans. The unpleasant sounds are called noise.

Unwanted or excessive sounds lead to noise pollution.

Two effects of noise pollution are – Temporary or permanent impairment of hearing and sleep disruption.

a) A: Sounds of frequencies less than about 20 vibrations per secondare called inaudible.

R: Sounds of frequencies less than about 20 vibrations per second cannot be detected by the human ear.

I.) Both A and R are true and R is the correct explanation of A.

II.) Both A and R are true but R is not the correct explanation of A.

III.) A is true but R is false.

IV.) A is false but R is true.

V.) Both A and R are false.

Ans. I. Both A and R are true and R is the current explanation of A.

b) A: Silencing devices must be installed in air craft engines, transport vehicles, industrial machines and home appliance.

R: Attempts should be made to minimize noise pollution.

I.) Both A and R are true and R is the correct explanation of A.

II.) Both A and R are true but R is not the correct explanation of A.

III.) A is true but R is false.

IV.) A is false but R is true.

V.) Both A and R are false.

Ans.I. Both A and R are true and R is the current explanation of A.

5) Sounds of frequencies less than about 20 vibrations per second cannot be detected by the human ear. Such sounds are called inaudible. On the higher side, sounds of frequencies higher than about 20,000 vibrations per second are also not audible to the human ear. Thus, for human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz. Some animals can hear sounds of frequencies higher than 20,000 Hz. Dogs have this ability. The police use high frequency whistles which dogs can hear but humans cannot.

a) For human ear, the range of audible frequencies is roughly from ______ Hz. (20 to 20,000 Hz)

b) Sounds of frequencies less than about _____ vibrations per second cannot be detected by the human ear.(20)

c) _____ have the ability to hear sounds of frequencies higher than 20,000 Hz. (Dogs)

### More Extra Questions and Answers

Q.1) Fill in the blanks

1) Do an from motion of an object is called vibration.

2) Manjira, Gotham are types of musical instruments commonly used in many parts of our country.

3) Amplitude and frequency are two important properties of sound.

4) Frequency determines the pitch of sound.

5) Loudness of sound is proportional to the square of theamplitude of the vibration producing the sound.

6) Larger the amplitude of vibration louder is the sound

Q.2) Say whether the following statements are true or false

1) Pleasant sounds are called as noise .

Ans : False

2) Sound is produced by vibrating objects.

Ans: True

3) The frequency is expressed in Hertz.

Ans :True

In case you are missed :- Previous Chapter Extra Questions

4) In order to control noise we must control the sources of noise.

Ans :True

5) Dogs can hear sounds of frequencies higher than 20,000 Hertz.

Ans :True

6) Sounds of frequencies less than 10 vibrations per second cannot be detected by human ear.

Ans :False

Q.3) Define the following

1) Noise

Ans : Unpleasant sounds are called noise.

2) Decibel

Ans :You need to use to express the loudness is called as decibel.

3) Oscillatory motion

Ans :Two and promotion of an object is known as vibration this motion is called as oscillatory motion.

4) Frequency of oscillation

Ans : The number of oscillations per second is called the frequency of oscillation.

5) Ear drum

Ans :When sound enters it travels down a canal at the end of which there is a thin stretch membrane it is called eardrum.

6) Vibration

Ans :To and froand back and forth motion of an object is call vibration.

1) How is sound produced?

Ans :When in tightly stretchy band is plugged it vibrates and produces the sound.

2) Name any two commonly used musical instruments in our country.

Ans :Manjira, mud pot , GH ATM  are some of the commonly used musical instruments in our country.

3) How can we hear a sound?

Ans :When sound enters it travel down again let the end of which there is athene’s rich membrane gold eardrum. your room is like a stretch rubber sheet. sound vibrations make the year drum vibrate. Do your drum sense vibration to the inner ear. From there signal goes to the brain. That is how we hear.

4) Differentiate with two points difference between noise and musical sound.

 NOISE MUSICAL SOUND Noise is an unpleasant sound sounds that we get from musical instruments are called as musical sound Noise is unpleasant for ear musical sound is pleasing to the ear Example. construction work going in neighbourhood, horns of buses and trucks. Example. sound produced by a harmonium is a musical sound.

5) What is noise pollution and causes of noise pollution?

Ans :a)Presence of excessive or unwanted sounds in the environment is called noise pollution.

b) Major causes of noise pollution are

i) sounds of vehicles machines bursting of crackers loud speakers etc

ii)television and transistor radio at high volumes, kitchen appliances, cooler, air conditioner  are also some of the measures of noise pollution.

In case you are missed :- Next Chapter Extra Questions

Updated: April 5, 2023 — 12:15 pm