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 physics superposition of waves coherence young's double slit experiment interference

Statement-1: All points on a wavefront vibrate in same phase with same frequency
Statement-2: Two sources are said to be coherent if they produce waves of same frequency with a constant phase difference.

  1. Statement-1 is false, Statement -2 is true

  2. Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1

  3. Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for statement-1

  4. Statement-1 is true, Statement-2 is false
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

All points on the wavefront have the same temporary displacement. Then need not be oscillating with the same frequency and constant phase difference.
Two wave sources are said to be coherent if they produce waves of same frequency and constant phase difference.
Hence assertion is incorrect, reason is correct. Option A.

Multiple choice physics superposition of waves coherence young's double slit experiment interference

To demonstrate the phenomenon of interference of sound, we need:

  1. two sources, which emit sound of exactly the same frequency

  2. two sources, which emit sound of exactly the same frequency and have a definite phase relationship

  3. two sources, which emit sound of exactly the same frequency and have a varying phase relationship

  4. two sources, which emit sound of exactly the same wavelength
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For demonstration of interference of sound we need two coherent  source, of same frequency with constant phase difference

$P _1=P _{01}  sin  (Kx-\omega t)$

$P _2=P _{02}  sin  (k(x+\Delta x)-\omega t)$

$=P _{02}  sin  (Kx-\omega t+\delta )$

$\delta =K\Delta x=\dfrac{2\pi \Delta x}{\lambda }$

Multiple choice civics road safety rules and regulations road safety education general awareness road safety

Drivers of vehicles shall not use the _____.

  1. Sound of the horn should not be more needlessly

  2. Drivers should avoid sound of horn in silence zones

  3. Drivers should not drive which have mechanical defect

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All the given options are to be followed while driving. They include: Horn should not be used more needlessly, as it cause irritation and sound pollution. It should not be used in silent zones like near hospitals and schools as it may cause disturbance and recklessness. Vehicles with mechanical defects should not be used at all.

Multiple choice geography pollution - types and sources study of water pollution threats to water resource major hazards in india and prevention

__________ is an unwanted sound that is an irritant and source of stress.

  1. Soil pollution

  2. Water pollution

  3. Noise pollution

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Noise can be defined as an unpleasant and unwanted sound. Noise pollution affects both health and behavior. Unwanted sound (noise) can damage psychological health. Noise pollution can cause hypertension, high stress levels, tinnitus, hearing loss, sleep disturbances, and other harmful effects.

Sound becomes unwanted when it either interferes with normal activities such as sleeping, conversation, or disrupts or diminishes one's quality of life

Multiple choice physics oscillatory motion motion of a mass suspended by two springs example of simple harmonic motion oscillations due to a spring

A hollow pipe of length $0.8\ m$ is closed at one end. At its open end, a $0.5\ m$ long uniform string is vibrating in its second harmonic and it resonates with the fundamental frequency of the pipe. If the tension in the wire is $50\ N$ and the speed of sound is $320\ ms^{-1}$, the mass of the string is

  1. $5\ grams$
  2. $10\ grams$
  3. $20\ grams$
  4. $40\ grams$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Velocity of sound $= c$

$\dfrac{c}{4L} = \dfrac{2v}{l}$

$\Rightarrow \dfrac{320}{4\times 0.8} = \dfrac{1}{5} \sqrt{\dfrac{T}{\mu}}$

$\Rightarrow \mu = 0.02\space kgm^{-1}$

$\Rightarrow m = \mu l = 10\space g $

 

Multiple choice

Active listening can be shown in different ways.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Active listening involves fully concentrating, understanding, responding, and remembering what is being said. It can be demonstrated through verbal cues, such as paraphrasing, and non-verbal cues, such as nodding or maintaining eye contact.

Multiple choice intensity and loudness waves physics

The power of sound from speaker of radio is 10 W, the power of sound from the speaker of radio is 400 W by increasing the volume of radio. The power increased in dB as compared to original power is nearly

  1. 8

  2. 12

  3. 13

  4. 16
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The increase in decibels is calculated as 10 * log10(P2/P1). Here, 10 * log10(400/10) = 10 * log10(40) = 10 * 1.602 = 16.02 dB.

Multiple choice intensity and loudness waves physics

State the factors that determine the loudness of the sound heard.

  1. Amplitude

  2. Freqency

  3. Time period

  4. Pitch
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Amplitude is the size of the vibration, and this determines how loud the sound is Larger vibrations make a louder sound.The intensity or loudness of a sound depends upon the extent to which the sounding body vibrates, i.e., the amplitude of vibration. A sound is louder as the amplitude of vibration is greater, and the intensity decreases as the distance from the source increases. Hence, loudness is dependent on amplitude.

Multiple choice intensity and loudness waves physics

Name the characteristic of the sound affected due to a change in its amplitude.

  1. Loudness.

  2. Wavelength.

  3. Frequency.

  4. Waveform.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Amplitude is the size of the vibration, and this determines how loud the sound is.  Larger vibrations make a louder sound.
The intensity or loudness of a sound depends upon the extent to which the sounding body vibrates, i.e., the amplitude of vibration. A sound is louder as the amplitude of vibration is greater, and the intensity decreases as the distance from the source increases.
Hence, loudness of the sound is affected due to the change in its amplitude.

Multiple choice intensity and loudness waves physics

As we move away from the source along with the amplitude which of the following quantity decreases as well ?

  1. waveform

  2. loudness

  3. wavelength

  4. intensity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The intensity or loudness of a sound depends upon the extent to which the sounding body vibrates, i.e., the amplitude of vibration. A sound is louder as the amplitude of vibration is greater, and the intensity decreases as the distance from the source increases. Loudness is measured in units called decibels. 
Loudness depends on the square of the amplitude of the wave. That is, $loudness{ \propto \left( amplitude \right)  }^{ 2 }$.
Hence, As it moves away from the source its amplitude as well as its loudness decreases.

Multiple choice intensity and loudness waves physics

By reducing the amplitude of a sound wave, its :

  1. Pitch increases

  2. Loudness decreases

  3. Loudness increases

  4. Pitch decreases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The loudness of sound is directly proportional to amplitude of sound wave. 


loudness $\propto$ amplitude

Hence on reducing amplitude the loudness also decreases. 

Multiple choice intensity and loudness waves physics

Unit for measuring the loudness of sound is _________________.

  1. Decibel

  2. Pascal

  3. Newton

  4. Newton-metre
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Unit for measuring the loudness of sound is decibel.
The intensity or loudness of a sound depends upon the extent to which the sounding body vibrates, i.e., the amplitude of vibration. A sound is louder as the amplitude of vibration is greater, and the intensity decreases as the distance from the source increases. Loudness is measured in units called decibels. 

Multiple choice intensity and loudness waves physics

Sound levels are measured in

  1. Decimeters

  2. Decibels

  3. Deciliters

  4. Decigrams
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.

The intensity or loudness of a sound depends upon the extent to which the sounding body vibrates, i.e., the amplitude of vibration. A sound is louder as the amplitude of vibration is greater, and the intensity decreases as the distance from the source increases.
Sound levels is measured in units called decibels. 

Multiple choice intensity and loudness waves physics

If the amplitude of the sound is made 3 times its initial value, then its loudness will become _______________ times its initial value.

  1. 9

  2. 4

  3. 16

  4. 25
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If the amplitude of the sound is made 3 times its initial value, then its loudness will become nine times its initial value.
Loudness depends on the square of the amplitude of the wave. 
That is, $Loudness\propto { (Amplitude) }^{ 2 }$.
Thus, when amplitude of the wave is tripled, the loudness increases nine times.

Multiple choice intensity and loudness waves physics

The loudness of sound is measured in _______ .

  1. decibels

  2. metres

  3. kilograms

  4. seconds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The loudness of sound is measured in units called decibels (dB). A decibel unit expresses the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 100 dB, which is near the level most people find uncomfortably loud.