Physics · Science General

Acoustics and Sound Waves

2,006 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 propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The sound of lightning flash is heard $3$ second after the flash is seen. The distance of the lightning is $1020$ metre. The speed of sound is:

  1. $1400\ m/s$
  2. $332\ m/s$
  3. $340\ m/s$
  4. $none\ of\ these$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given data,
Distance $d=1020 m$
Time $t=3s$
Speed$=?$
$Speed=\dfrac{distance }{time}=\dfrac{1020}{3}=340 m/s$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The speed of sound in air is  330m/s. It takes 10s for sound to reach a certain distance from the source placed in air. Find the distance.

  1. 669m

  2. 330m

  3. 3300m

  4. 1200m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\displaystyle V=330{ m }/{ s },t=2s,V=\frac { d }{ t } $
$\displaystyle d=V\times t$
$\displaystyle =330\times 10=3300m$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

On a hot, dry summer day a boy is standing between plane parallel vertical cliffs separated by $75m$. He is $30$m away from one of the cliffs. Consider speed of sound in air on that hot day to be $360m/s$. The boy claps loudly and hearts its successive echoes. The time in seconds at which he hears the first four echoes are respectively

  1. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{5}{12}, \frac{5}{12}$
  2. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{7}{12}, \frac{2}{3}$
  3. $\displaystyle \frac{1}{4}, \frac{1}{3}, \frac{5}{12}, \frac{5}{12}$
  4. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{1}{3}, \frac{5}{12}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

First echo : When sound goes to the cliff 1 and returns to his ear

Distance traveled by sound, $S = 30+30 = 60$ m
Time taken, $t _1 = \dfrac{60}{360} = \dfrac{1}{6}$ s

Second echo : When sound goes to the cliff 2 and returns to his ear
Distance traveled by sound, $S = 45+45 = 90$ m
Time taken, $t _2 = \dfrac{90}{360} = \dfrac{1}{4}$ s

Third echo : When the reflected sound from cliff 1 goes to the cliff 2 and returns to his ear
Distance traveled by sound, $S = 30+75+45 = 150$ m
Time taken, $t _3 = \dfrac{150}{360} = \dfrac{5}{12}$ s

Fourth echo : When the reflected sound from cliff 2 goes to the cliff 1 and returns to his ear
Distance traveled by sound, $S = 45+75+30 = 150$ m
Time taken, $t _4 = \dfrac{150}{360} = \dfrac{5}{12}$ s

Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

A metal hammer hits a spherical bell, when the circuit in a calling bell is switched ON, the propogation of sound takes place due to 

  1. Air

  2. electric current

  3. metal bell

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

Though the hammer strikes the bell and the bell starts vibrating, these vibrations are then carried out to the atmosphere only by air molecules thereby creating a sound

The correct option is (a)

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

The waves produced by the horn of a car consists of

  1. Alternate crests and troughs

  2. Alternate crests and compressions

  3. Alternate rarefactions and compressions

  4. Alternate troughs and rarefactions
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sound waves produced by a car horn are longitudinal waves traveling through the air. Longitudinal waves consist of alternate regions of compression, where particles are closely packed, and rarefactions, where particles are spread apart. They do not contain crests and troughs, which are features of transverse waves.

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

While travelling by train, when the train passes through the tunnel, why does our ear aches ?

  1. atmospheric pressure

  2. tunnel pressure

  3. water pressure

  4. None of the above

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a train enters a tunnel, it compresses the air in front of it like a piston. Unlike outside air, air in a tunnel can’t be simply pushed aside—the tunnel walls are in the way. Some of the air is pushed forward, all the way down to the tunnel’s other end, but most of it rushes through the narrow space between the train and the tunnel walls, filling in the area behind the train. Being forced into this narrow space makes the air rush faster, exactly as water speeds up at the base of a funnel. In fact, this tunnel air can rush backward much faster than the train’s forward speed. his fast moving air creates a kind of suction on the train, lowering the air pressure inside and making your ears go pop. It cause ear aches

Hence, due to sudden increase and decrease pressure inside tunnel, aches occur in ear 

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

The buzzing sound produced by a mosquito is produced by:

  1. its mouth

  2. vibration of sorrunding air

  3. vibration of wings

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

$Answer:-$ C

The noise from a mosquito comes from its wing beat. since the sound is of low intensity, attrition is quick to set in over even short distances and we would hear it only if its close to our ears. it is the high pitch of the sound that probably makes it so irritating.

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

Thermocol is a:

  1. good reflector of sound

  2. good absorber of sound

  3. bad absorber of sound

  4. good conductor of sound
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Materials which are soft , porous and have a high sound absorption coefficient , are good absorber of sound , thermocol has these qualities , so it is a good absorber of sound .

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

The amplitude of vibration and its frequency can change suddenly in a:

  1. pitch

  2. musicalsound

  3. noise

  4. all of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pitch is a characteristic of sound , which depends upon frequency and amplitude of vibration doesn't affect it .

A musical sound has , regular and discrete frequencies , sudden change in amplitude and frequency will make it unpleasant , so it doesn't happen in musical sound .
Noise is a mixture of irregular and continuous frequencies , which has sudden change in amplitude and frequency . 

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

In the following sentence. say 'True' and 'False'
$(a)$ Sound can't travel in vacuum (T/F)
$(b)$ The number of oscillations per second of a vibrating object is called its time period. (T/F)
$(c)$ If the amplitude of vibration is large, sound is feeble. (T/F)
$(d)$ For human ears, the audible range is 20Hz to 20,000Hz. (T/F)
$(e)$ The lower the frequency of vibration, the higher is the pitch.
$(f)$ Unwanted or unpleasant sound is termed as music. (T/F)
$(g)$ Noise pollution may cause partial hearing impairment. (T/F)

  1. $TFTTFFT$
  2. $TTFTFFT$
  3. $TFFTFFF$
  4. $TFFTFFT$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Below are the answers and the corresponding explanations.

(a) True. Sound requires a medium to travel through. Since vacuum is devoid of any medium, sound cannot travel through it.

(b) False. The number of oscillations per second of a vibrating object is known as its frequency. Time period is the time
required to complete one oscillation.

(c) False. Loudness of a sound is proportional to the square of the amplitude of its vibration. When the amplitude of
vibration of a sound is large, the sound is very loud. The sound is feeble for small amplitude.

(d) True. Humans cannot hear sounds of all frequencies. Human can hear a sound whose frequency falls in the range of
20 Hz - 20,000 Hz. The sound having frequency out of this range is inaudible to humans.

(e) False. The pitch of a sound is proportional to its frequency. As the frequency of vibration increases,
the pitch of the sound also increases and vice versa. A sound is said to be high pitched if its frequency of vibration is high
and is low pitched for a small frequency of vibration.

(f) False. Unwanted or unpleasant sounds are known as noise. Sounds that are melodious and pleasing to ear are known as music.

(g) True. Unwanted or unpleasant sounds are known as noise. If one is subjected to loud unpleasant sound
continuously for a long time, then it may cause temporary hearing impairment.

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

Unpleasant sound : Noise : : Pleasant sound :______. Fill in the blank. 

  1. Audible sound

  2. Infrasound

  3. Music

  4. Ultrasound
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sounds that are unpleasing and disturbing to the ears are called noise, whereas, the pleasing and comforting to the ears are called music, like those produced by musical instruments.