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 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.

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

To reduce noise pollution, which of the following devices must be installed on the vehicles ?

  1. Lights

  2. Speedometer

  3. Horn

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

Lights in a vehicle are used to experience the  view ahead of vehicle , in low light .

Speedometer is used to measure the speed of vehicle .
Horn is used to signal other vehicles , and a horn produces noise pollution .
Silencer in a vehicle is used to reduce the sound of the engine of vehicle , therefore it must be installed on the vehicles to reduce noise pollution .

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

The waveform of noise sound is 

  1. Irregular

  2. Sudden

  3. Periodic

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Music is a pleasant sound, whereas noise is unpleasant to hear. The waveform of musical sound is periodic and regular whereas the waveform of noise is irregular and sudden.
The frequencies that make up a musical sound are in the ratio of small whole numbers whereas this is not the case for noise.

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

If the density of  sound is increased by a factor of 100, by how many decibles is the sound level increased?

  1. 100 dB

  2. 1000 dB

  3. 20 dB

  4. 30 dB
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The decibel level change is calculated using the formula delta dB = 10 * log10(I2/I1). Since the intensity (or density of sound energy) increases by a factor of 100, the change is 10 * log10(100) = 10 * 2 = 20 dB.