# Samacheer Kalvi Class 8 Science Unit 6 Sound Solutions

## Samacheer Kalvi Class 8 Science Unit 6 Sound Solutions

Welcome to NCTB Solutions. Here with this post we are going to help 8th class students by providing Solutions for Samacheer Kalvi Class 8 Science Unit 6 Sound. Here students can easily find all the solved solution for Sound Exercise questions. Also here our Expert Science Teacher’s solved all the questions with easily understandable language with proper guidance so that all the students can understand easily. Here on this post students will get Unit 6 Sound exercise solutions. Here all the solutions are based on Tamil Nadu State Board latest syllabus.

#### Unit 6 Sound Exercise Questions Solutions :

(1) Sound waves travel very fast in

(a) air

(b) metals

(c) vacuum

(d) liquids

Correct Option → (d)

Sound waves travel very fast in Liquids.

(2) Which of the following are the characteristics of vibrations?

(i) Frequency

(ii) Time period

(iii) Pitch

(iv) Loudness

(a) i and ii

(b) ii and iii

(c) iii and iv

(d) i and iv

Correct Option → (a)

Frequency and Time period.

(3) The amplitude of the sound wave decides its

(a) speed

(b) pitch

(c) loudness

(d) frequency

Correct Option → (c)

The amplitude of the sound wave decides its Loudness.

(4) What kind of musical instrument is a sitar?

(a) String instrument

(b) Percussion instrument

(c) Wind instrument

(d) None of these

Correct Option → (a)

Sitar is a string type musical instrument.

(5) Find the odd one out.

(a) Harmonium

(b) Flute

(d) Violin

Correct Option → (d)

Here the odd one is Violin.

(6) Noise is produced by

(a) vibrations with high frequency.

(b) regular vibrations.

(c) regular and periodic vibrations.

(d) irregular and non-periodic vibrations.

Correct Option → (d)

Noise is produced by Irregular vibrations.

(7) The range of audible frequency for the human ear is

(a) 2 Hz to 2000 Hz

(b) 20 Hz to 2000 Hz

(c) 20 Hz to 20000 Hz

(d) 200 Hz to 20000 Hz

Correct Option → (c)

The range of audible frequency for the human ear is 20 Hz to 20000 Hz.

(8) If the amplitude and frequency of a sound wave are increased, which of the following is true?

(a) Loudness increases and pitch is higher.

(b) Loudness increases and pitch is unchanged.

(c) Loudness increases and pitch is lower.

(d) Loudness decreases and pitch is lower.

Correct Option → (a)

Loudness increases and pitch is higher.

(9) Which of the following may be caused by noise?

(a) Irratition

(b) Stress

(c) Nervousness

(d) All the above

Correct Option → (d)

All of the above may be caused by noise.

(II) Fill in the blanks

(1) Sound is produced by ____

(2) The vibrations of a simple pendulum are also known as ____

(3) Sound travels in the form of ____

(4) High frequency sounds that cannot be heard by you are called ____

(5) Pitch of a sound depends on the ____ vibration.

(6) If the thickness of a vibrating string is increased, its pitch ____

(1) → Vibration of the particles

(2) → Oscillation

(3) → Waves

(4) → Ultra sonic sound

(5) → Frequency of vibrating body

(6) → Low

(1) What is vibration?

Vibration means a kind of to and fro motion of a particle. This to and fro motion causes vibrations.

(2) Give an example to show that light travels faster than sound?

When lighting strikes the sound is heard a little after by light it means light travels faster than sound it means light travels faster than sound.

(3) To increase loudness of sound by four times, how much should the amplitude of vibration be changed?

To increases loudness of sound by four times amplitude should be increases twice of the of loudness.

(4) What is an ultrasonic sound?

A sound with a frequency greater than 20000 Hz is called ultrasonic sound.

(5) Give two differences between music and noise.

Music :

The sound that provides a pleasing sensation to the ear is called music .

Music is produced by musical instruments like sitar, veena which feel us happy.

Noise :

The sound that unpleasant to the ear is called noise.

Noise is harmful to us it produced disturbance to our ear.

(6) What are the hazards of noise pollution?

The sound is that is unpleasant to the ear is called noise, and the disturbance produced in the environment by loud and harsh sounds from various sources is known as sound pollution. There are some hazards of sound pollution to our health like loud noise causes heart attack and unconsciousness. Noise pollution causes loss of hearing, affects person’s peace of mind etc. are the hazards of noise pollution.

(7) Mention few measures to be taken to reduce the effect of noise pollution.

Few measure to be taken to reduce noise pollution are following-

(a) Strick guidelines should be set for the use of loudspeakers on social, religious and political occasions.

(b) Industrial machines and home appliances should be properly maintained.

(c) People working is noisy factories should wear ear plugs.

(d) Residential area should be free from heavy vehicles.

(e) All communication systems must be operated in low volumes

(1) Describe an experiment to show that sound cannot travel through vaccum.

As we know that the sound required a medium for its propagation it can not be travel from a vaccum to understand this see the following experiment

Take a bell jar and a mobile phone switch on the music in the mobile phone and place it in the jar. Now pump out the air from the bell jar using a vaccum pump. As more and more air is removed from the jar, the sound from the mobile phone becomes feebler and finally very faint. From this it is clear that sound required a medium for its propagation it cannot travel from the vaccum medium. It required a medium like air, water, solid etc. but not travel in vacuum medium.

(2) What are the properties of sound?

There are some properties of sound as following :

(a) Loudness : it is defined as the characteristics of a sound that enables us to distinguish a weak and feeble sound from a loud sound. The loudness of a sound depends on its amplitude. Higher the amplitude louder will be the sound and vice versa. The loudness of a sound is measure in decibel.

(b) Pitch : it is the characteristics of sound that enables us to distinguish between a flat sound and a shrill sound. Higher the frequency of sound higher will be the pitch. The voice of female has a higher pitch and male has lower pitch. Therefore female voice is shrill than male voice.

(c) Quality or timbre : it is the characteristic of sound that enables us to distinguish between two sounds that have the same pitch and amplitude.

(d) Audibility of sound : it is classify into three types-

(1) Audible sound : sound with frequency from 20 Hz to 20000 Hz is called sonic sound or audible sound . human ears cannot hear sound below the frequency 20 Hz to 20000 Hz.

(2) Infrasonic sound : a sound with frequency below 20 Hz called infrasonic sound. Humans cannot hear this sound. Dog ,dolphin etc can hear this sound.

(3) Ultrasonic sound : a sound with frequency greater then 20000 Hz is called ultrasonic sound. Animals like dog, cat, dolphin etc can hear this sound.
This are the properties of sound.

(3) What steps should be taken to reduce the effect of noise pollution?

Few measure to be taken to reduce noise pollution are following: –

(a) Strict guidelines should be set for the use of loudspeakers on social, religious and political occasions.

(b) Industrial machines and home appliances should be properly maintained.

(c) People working is noisy factories should wear ear plugs.

(d) Residential area should be free from heavy vehicles.

(e) All communication systems must be operated in low volumes.

(f) People should be increases to plant trees and use absorbing to materials like curtains and cushions in their home.

(g) This are some measure to take to reduce noise pollution.

(4) Describe the structure and function of the human ear?