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 sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

A sound wave has a frequency of $10$kHz and wavelength $3$mm. How much time will it take to travel $3$ metre?

  1. $0.1$ sec
  2. $1$ sec
  3. $10$ sec
  4. $0.01$ sec
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$V=f\times \lambda$
$=10\times 10^3\times 3\times 10^{-3}=30$
$t=\displaystyle\frac{d}{v}=\frac{3}{30}=0.1$sec.

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

The total energy of sound waves E is related to their frequency n as

  1. $E \propto n$
  2. $E \propto \dfrac{1}{n}$
  3. $E \propto \dfrac{1}{n^2}$
  4. $E \propto \dfrac{1}{log n}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy of a wave is related to its frequency using the formula E = hf, f is the frequency of the wave

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

Two tuning forks of frequency 256 and 258 vibrating per second are sounded together, then time interval between consecutive maxima heard by the observer is.

  1. 2 sec

  2. 1 sec

  3. 0.5 sec

  4. 1/4 sec
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\begin{array}{l} { n _{ 1 } }=256 \ { n _{ 2 } }=258 \ Both\, tuning\, forks\, are\, making\, beats \ so,\, we\, know\, that \ { t _{ \left( { for\, \, \max  . } \right)  } }=\dfrac { 1 }{ { { n _{ 2 } }-{ n _{ 1 } } } } \sec   \ =\dfrac { 1 }{ { 258-256 } }  \ =0.5\, \sec   \end{array}$

Hence, the option $C$ is the correct answer.

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

If the frequency of sound wave in air is doubled, its wavelength.

  1. is doubled

  2. increases 4 times

  3. decreases 4 times

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

Answer is D.

A sound wave has a speed that is mathematically related to the frequency and the wavelength of the wave. The mathematical relationship between speed, frequency and wavelength is given by the following equation.
Speed = Wavelength * Frequency
That is, Frequency = speed / Wavelength. The frequency and wavelength are inversely proportional to each other.
So, when the frequency is doubled, the wavelength will be halved.

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

The time period of a sound wave from a piano is $1.18\times10^{-3} s$. Find its frequency.

  1. $847.45 Hz$
  2. $800 Hz$
  3. $935. 55 Hz$
  4. $1000 Hz$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The frequency (f) of a wave is the number of full wave forms generated per second. This is the same as the number of repetitions per second or the number of oscillations per second.  
Time Period (T) is the number of seconds per waveform, or the number of seconds per oscillation.  It is clear that frequency and period are reciprocals. 
In this case, the time period is given as $1.18\times { 10 }^{ -3 }s$.
So, the frequency $f=\frac { 1 }{ t } =\frac { 1 }{ 0.00118s } =847.45Hz.$

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

If a vibrator strikes the water $50$ times in $5s$, then the frequency of wave is

  1. $10 Hz$
  2. $0.5 Hz$
  3. $5 Hz$
  4. $0.1 Hz$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Total number of vibrations, in $5s$ is $50$.
So, number of vibrations in $1s$ is $\dfrac{50}{5}=10$
Frequency$=10Hz$
Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

One sound wave strikes a person's ear every $1/100$ of a second. The speed of sound where the person is located is $345 m/s$.
What is the frequency of the sound?

  1. $3.45\ Hz$
  2. $34,500\ Hz$
  3. $0.01\ Hz$
  4. $100\ Hz$
  5. $2.9\ Hz$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Time period of sound wave       $T = \dfrac{1}{100}$ second


$\therefore$ Frequency of sound wave      $\nu = \dfrac{1}{T} =100$  $Hz$

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

If you go on increasing the stretching force on a wire in a guitar, its frequency

  1. Increases

  2. Decreases

  3. Remains unchanged

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a stretching force is applied to a string or a wire, it applies a restoring force in the opposite direction. This force tends to bring the wire in its original length. It is known as tension in wire.

When we apply a stretching force on the wire of a guitar, the wire applies tension backwards. Greater the stretching force, greater is the tension.
The frequency of vibration of a stretched wire is directly proportional to the square root of the tension in it.
Hence on increasing the stretching force on a wire in a guitar, its frequency increases

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

The sounds having frequency of $20$ Hz to $20,000$ Hz are

  1. Ultrasound

  2. Infrasonics

  3. Hypersonics

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

In the case of sound waves, having frequency in between $20$ Hz and $20,000$ Hz, called audible sound and  waves of frequency smaller than $20$ Hz are called infrasonic and waves having frequency greater then $20,000$ Hz, called Hypersonics sounds.

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

An oscillator is producing FM waves of frequency 2kHz with avariation of 10kHz. The modulating index=?

  1. 0.20

  2. 5.0

  3. 0.67

  4. 1.5
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Modulation Index , $m _f=\dfrac{\text{Maximum frequency deviation}}{\text{Modulating frequency}}$

$\Rightarrow m _f= \dfrac{10 kHz}{2 kHz}$
$\Rightarrow m _f=5$

Multiple choice evs the unique world of insects and animals sleeping time animal senses sense organs in animals sense organs in humans

The stato-acoustic receptor responds to changes in the ..................

  1. Light and pressure

  2. Pressure and touch

  3. Pain and pressure

  4. Sound and equilibrium.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statio-acoustic receptors are meant for both sensory functions, i.e., hearing (sound) and maintenance of body balance (equilibrium) of the body. These receptors generate stimuli in response to sound and gravity. The function of  stato-acoustic receptor is hearing and balancing.


Multiple choice chemistry metals physical properties of metals and non-metals some physical properties of metals general characteristics and uses of metals

The property of metals producing a ringing sound when struck is called :

  1. sonority

  2. permeability

  3. ductility

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

Sonority (of a material) is the property of producing a ringing sound when struck. Most metals are sonorous. Therefore, they are used in many instruments (eg. cymbals and bells). Almost all non-metals are non-sonorous, i.e. they don't produce a ringing sound when struck.


Hence, the correct option is $\text{A}$

Multiple choice physics wave motion wave velocity speed and acceleration of travelling wave speed of a travelling wave

A certain strings will resonate to several frequencies , the lowest of which is $200$cps.what are the next three higher frequencies to which it resonates? 

  1. $400,600,800$
  2. $300,400,500$
  3. $100,150,200$
  4. $200,250,300$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Given,  The Lowest frequency is $200cps$

Let  $f$ resonant the fundamental frequency, then the next higher frequency is: $2f,3f,4f$

$2\times200=400cps,3\times200=600,4\times200=800cps$