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 time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

The walls of the auditorium built for musical concerts should be such  that they are able to ______ sound. Fill in the banks.

  1. Transmit

  2. Refract

  3. Reflect

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

The walls of the auditorium should be equipped with good absorbing material , otherwise sound waves coming back after reflection from different walls may produce interference , constructive interference at any place in auditorium will produce a loud sound whereas distructive interference at any place in auditorium will produce a faint sound , making the music unpleasant . 

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

The _________ of sound depends on amplitude of vibration of the source.

  1. loudness

  2. pitch

  3. timbre

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

The loudness of sound depends on amplitude of vibration of the source. Loudness of sound is directly proportional to the square of the amplitude of vibration producing the sound.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

The more the amplitude of a vibrating body the more is the loudness. True or false.

  1. True

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

The amplitude of a sound wave determines its loudness. Sound wave with a large amount of energy have a larger amplitude which increases the loudness in the wave. A large amplitude means a louder sound and a smaller amplitude means a softer sound.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

Mark the incorrect statements.
(a) intensity of sound depends on the response of our ears
(b) loudness can be measured as a physical quantity
(c) loudness is a subjective quantity.

  1. a, b

  2. a, c

  3. b, c

  4. all of them
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Intensity of sound is an objective quantity. It does not depend on the response of our ears. 
Loudness is a subjective quantity. It cannot be measured as a physical quantity.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

A device based on multiple reflection used for sending amplified sound in a particular direction

  1. Bulb horn

  2. Megaphone

  3. Ear trumpet

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

Megaphone is based on multiple reflection of sound. It is a horn shaped tube designed to send amplified sound in a particular direction. It is also called Loud hailer.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

Mark the incorrect statement :

 a)intensity of sound depends on the response of our ears 

b)loudness can be measured as a physical quantity 

c)loudness is a subjective quantity. 

  1. a,b

  2. a,c

  3. b,c

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

Intensity of sound is an objective quantity. It does not depend on the response of our ears. Loudness is a subjective quantity. It cannot be measured as a physical quantity.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

How does Sound produced by humans?

  1. In humans sound is produced by the voice box

  2. In humans sound is produced by the larynx

  3. In humans sound is produced by the upper part of the wind pipe.

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

In humans sound is produced by the vioce box or larynx. It is the upper part of the wind pipe. Two vocal cords are stretched across the voice box leaving a narrow slit. When the lungs force air through the slit, it vibrates and produces sound.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

The greater the surface area of the vibrating body, the________is the loudness of sound.

  1. Lesser

  2. Greater

  3. Remains same

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

Loudness of the sound  $L = 10 \log _{10} \dfrac{I}{I _o}$

where $I$ is the intensity of sound.
Greater the surface area of the vibrating body, lesser will be the amplitude of the sound and thus lesser will be the intensity of the sound.

Thus lesser will be the loudness of sound.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

When we increase the loudness of sound of a TV, the property of sound that changes is:

  1. Amplitude

  2. Frequency

  3. Wavelength

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

Loudness of sound is proportional to the intensity and amplitude of sound. So when we turn on the volume of tv, the amplitude of sound wave increases hence, loudness of sound increases 

So the answer is A.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

In order to reduce the loudness of a sound we have to:

  1. decrease its frequency of vibration of the sound

  2. increase its frequency of vibration of the sound

  3. decrease its amplitude of vibration of the sound

  4. increase its amplitude of vibration of the sound
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Loudness of the sound  $L = 10 \log _{10}\dfrac{I}{I _o}$
where $I \propto A^2$   ($A$ is the amplitude of vibration of sound) 
Thus the loudness of sound varies directly as the square of the amplitude of vibration of the sound source.
Hence, the in order to reduce the loudness of sound, we have to decrease the amplitude of vibration of the sound.
Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

A 1cm long vibrates with a fundamental frequency of 256Hz. If the length is reduced to 1/4cm keeping the tension unaltered, the new fundamental frequency will be

  1. 64

  2. 256

  3. 512

  4. 1024
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
We know that $n\alpha\cfrac{1}{l}$
Thus $\cfrac{n _2}{n _1}=\cfrac{l _1}{l _1}\\n _2=\cfrac{l _1}{l _2}(n _1)=\cfrac{1\times256}{(1/4)}=256\times4=1024Hz$