Class 10 Sound Mock Test (ICSE)

Topics in Sound

• Reflection of sound and echo
• Uses of echo and SONAR
• Natural, damped and forced vibrations
• Resonance
• Loudness, pitch and quality
• Noise pollution

Sound practice questions with answers

1. Q1Multiple choice·1 mark
   What does the acronym SONAR stand for?

   1. (a)Sound Navigation and Ranging
   2. (b)Sound Navigation and Reflection
   3. (c)Sound Natural Amplitude Reflection
   4. (d)Sonic Oscillation Navigation and Radar
   Show answer and step marks

   1. Correct option: (a)+1

   Answer: (a)
2. Q2Multiple choice·1 mark
   Which of the following is a direct health hazard associated with prolonged exposure to severe noise pollution?

   1. (a)Impairment of hearing and hypertension
   2. (b)Skin cancer and cataract formation in the eyes
   3. (c)Asthma and chronic bronchitis
   4. (d)Fluorosis of the teeth and bones
   Show answer and step marks

   1. Correct option: (a) Impairment of hearing and hypertension+1

   Answer: (a)
3. Q3Multiple choice·1 mark
   For an echo to be distinctly heard by a human ear, taking the speed of sound as $340\text{ m s}^{-1}$, the minimum distance between the source and the reflecting surface must be at least:

   1. (a)$68\text{ m}$
   2. (b)$34\text{ m}$
   3. (c)$17\text{ m}$
   4. (d)$1.7\text{ m}$
   Show answer and step marks

   1. Correct option: (c)+1

   Answer: (c)
4. Q4Multiple choice·1 mark
   Which of the following characteristics of a sound note depends directly on its frequency?

   1. (a)Loudness
   2. (b)Speed
   3. (c)Pitch
   4. (d)Quality
   Show answer and step marks

   1. Correct option: (c)+1

   Answer: (c)
5. Q5Long answer·4 marks
   (a) Define resonance as a special case of forced vibrations. [1] (b) Two tuning forks $A$ and $B$ of the same frequency $512\text{ Hz}$ are mounted on separate sound boxes. When fork $A$ is set into vibration, fork $B$ also starts vibrating. Name the phenomenon observed in fork $B$ and explain why it happens. [2] (c) State one difference between forced vibrations and resonance in terms of amplitude. [1]
   Show answer and step marks

   1. (a) Resonance is a special case of forced vibrations when the frequency of the externally applied periodic force is exactly equal to the natural frequency of the vibrating body, causing it to vibrate with a very large amplitude.+1
   2. (b) Phenomenon observed: Resonance.+1
   3. (b) Reason: The frequency of the sound waves from fork $A$ matches the natural frequency of fork $B$, causing fork $B$ to absorb maximum energy and vibrate in resonance with a large amplitude.+1
   4. (c) In forced vibrations, the body vibrates with a small amplitude under an external periodic force of any frequency, whereas in resonance, the body vibrates with a very large amplitude when the driving frequency equals its natural frequency.+1

   Answer: (a) Resonance is the special case of forced vibrations in which the frequency of the applied periodic force equals the natural frequency of the body, so it vibrates with a very large amplitude. (b) Resonance: the 512 Hz sound from A matches B's natural frequency, so B absorbs maximum energy and vibrates with large amplitude. (c) Forced vibrations at an unmatched frequency have a small amplitude; in resonance the amplitude is very large.
6. Q6Long answer·4 marks
   (a) What is meant by resonance? State the essential condition for resonance to take place. (b) A tuning fork is mounted on a wooden resonance box made for that fork. Explain why it produces a much louder sound compared to when it is struck and held in hand.
   Show answer and step marks

   1. Definition of resonance: It is a special case of forced vibration where the frequency of the applied periodic force is exactly equal to the natural frequency of the vibrating body, causing it to vibrate with a large amplitude.+1
   2. Condition for resonance: The frequency of the external periodic force must be equal to the natural frequency of the vibrating body.+1
   3. Mechanism of sounding box: The stem of the vibrating tuning fork is fixed to the wooden box, forcing the large volume of air enclosed inside the box and the large wooden surface to undergo forced vibrations.+1
   4. Resulting resonance: Because the natural frequency of the air column matches the frequency of the fork, resonance occurs, producing a loud and sustained sound due to a larger mass of air being set into vibration.+1

   Answer: (a) Resonance is the special case of forced vibration in which a body vibrates with a large amplitude because the frequency of the applied periodic force equals its natural frequency; condition: the two frequencies must be equal. (b) The fork forces the box and its air column to vibrate; as their natural frequency equals the fork's, resonance sets a large mass of air vibrating with large amplitude, giving a louder sound.

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