Physics · Science General

Acoustics and Sound Waves

2,160 Questions

Acoustics and sound waves deal with mechanical vibrations traveling through media like air and water. Key concepts include wave reflection, beats, echoes, the Mach number, and infrasound. These physics fundamentals are regularly tested in general science sections of multiple competitive exams.

Sound wave propagationEchoes and reflectionWave interferenceMach numberInfrasound frequency

Acoustics and Sound Waves Questions

Multiple choice

Consider the following statements:

  1. Sometimes a curved sound board may be placed behind the stage of an auditorium for the absorption of sound waves.
  2. Human heart produces 'lub' sound during contraction of heart.

Which of the given statements is/are true?

  1. Only (1)

  2. Only (2)

  3. Both (1) & (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statement (1) is wrong. The curved sound board is placed behind the stage of an auditorium so that the sound after reflecting from the sound board spreads evenly across the width of the auditorium. Statement (2) is correct. Human heart produces 'lub dub' sound with contraction and relaxation of heart, respectively.

Multiple choice

Consider the following statements:

  1. Bells are made of metal and not of wood because density of the metal is greater than that of wood.
  2. The same musical note is played on different instruments at same loudness. It produces different sensations on the ear due to their different quality of sound.

Which of the given statements is/are incorrect?

  1. Only (1)

  2. Only (2)

  3. Both (1) & (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

(I) Statement (1) is wrong. The reason behind the manufacturing of bell by using metals, not using wood, is that wood dampens vibrations while metals are elastic. (II) Statement (2) is correct. Quality (or timbre) of the sound is the sensation received by the ear due to 'waveform'. Different instruments produce different waveform, which affects the quality of sound.

Multiple choice

Consider the following statements:

  1. If a person inhales helium, the person speaks with low pitched voice.
  2. In hearing aid, microphone converts the electrical signal to sound signal.

Which of the given statements is/ are incorrect?

  1. Only (1)

  2. Only (2)

  3. Both (1) & (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statement (1) is wrong. If a person inhales helium, the person speaks with high pitched voice.

Sound moves at different speeds through different gases. As it is not a normal atmosphere, the sound moves faster, compressing the wavelength to a higher pitched noise. Statement (2) is wrong. In hearing aid, the sound is received by microphone by which sound signal converts to electrical signal.

Multiple choice

Which of the following statements is/are correct for Doppler’s effect?

(1) It is the change in frequency of sound wave for a listener moving relative to its source. (2) It is the reflection of sound, reaching the listener some time after the direct sound.

  1. Only (1)

  2. Only (2)

  3. Both (1) and (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement (1) is correct. Doppler’s effect is the change in frequency of sound waves for a listener moving relative to its source. Statement (2) is wrong. Reflection of sound, reaching the listener some time after the direct sound is called echo.

Multiple choice

Consider the following statements:

(1) With rise in temperature, the speed of sound decreases. (2) The speed of sound is greater in liquids than in solids. (3) Supersonic jet planes travel faster than the speed of sound.

Which of the given statements is/are incorrect?

  1. Only (1)

  2. Only (2)

  3. Only (1) and (2)

  4. Only (2) and (3)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  1. Statement (1) is wrong. The speed of sound increases with an increase in temperature due to an increase in average molecular velocity. 2. Statement (2) is wrong. The speed of sound is greater in solid than in liquids because the solids have higher density. 3. Statement (3) is correct. The jet planes that travel faster than the speed of sound is known as supersonic jet planes.
Multiple choice

Consider the following statements:

(1) Caruso is said to have shattered a crystal chandelier with his voice. This is based on the principle of reverberation. (2) If you repeatedly tap the side of a drinking glass with a spoon while filling it with water, you will notice that the pitch of the sound decreases.

Which of the given statements is/are correct?

  1. Only (1)

  2. Only (2)

  3. Both (1) and (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statement (1) is wrong. The shattering of crystal chandelier is based on the principle of resonance of sound. A driving force in tune with the natural frequency (sometimes known as the resonant frequency) of an oscillator can buildup larger amplitudes than the oscillator could alone. This buildup is known as resonance or sympathetic vibration.

Statement (2) is correct. If you repeatedly tap the side of a drinking glass with a spoon while filling it with water, you will notice that the pitch of the sound decreases. The length of the medium to travel the sound increases with the addition of water in glass and hence decreases the pitch of sound.

Multiple choice

Why does balloon burst with a sound when it is pricked with a needle?

  1. Because of force exerted by the needle.

  2. Because of force exerted by gas present in the balloon.

  3. Because of decreasing kinetic energy of gas.

  4. Because of high temperature inside the balloon.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The balloon bursts with a sound when it is pricked with a needle because of the force exerted by the gas present in the balloon.

Multiple choice

Consider the following facts about sound pollution:

  1. It is not the intensity, but the pitch of the sound which is of importance when measuring noise.
  2. A noise source measuring 70 decibels is 100 times as loud as a source measuring 50 decibels.

Which of the above is/are true?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Although the frequency (pitch) of noise may be of major importance, most noise sources are measured in terms of intensity or strength of the sound field. The standard unit, one decibel (dB), is the amount of sound that is just audible to the average human. The decibel scale is somewhat misleading because it is logarithmic rather than linear. For example, a noise source measuring 70 dB is 10 times as loud as a source measuring 60 dB and 100 times as loud as a source reading 50 dB.

Multiple choice

Choose the incorrect option out of the following.

  1. The tiger's whiskers can sense the movements or vibration in air.

  2. A tiger will avoid going into another tiger's area.

  3. A tiger's roar can be heard up to 6 kilometres.

  4. A tiger roars when it is angry and snarls to call out tigers.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A tiger's roar can be heard up to 3 kilometres.

Multiple choice

Consider the following statements:

  1. In aerodynamics, Mach number is related to the speed of the object to that of the speed of the sound.
  2. Tinnitus is the perception of sound within the human ear not including the perception of sound outside.

Which of the given statements is/are incorrect?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement 1 is correct. Mach number is a dimensionless quantity representing the ratio of speed of the object to that of the speed of the sound. Statement 2 is also correct. Tinnitus is a resultant condition of noise pollution. In this, patient perceives the ringing noise in his/her ears.