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

In which of the following mediums is the variation of speed of sound with temperature the greatest?

  1. Solid

  2. Liquid

  3. Gas

  4. Same in all cases
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gases show the greatest variation in sound speed with temperature because their particles are farther apart and temperature changes significantly affect molecular motion. In solids and liquids, particles are already tightly packed, so temperature has relatively less effect on sound speed.

Multiple choice

What should be the approximate minimum distance between the source and the reflector in air so that an echo is heard?

  1. 34 m

  2. 17 m

  3. 10 m

  4. 68 m
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For an echo to be distinct, the reflected sound must reach the ear at least 0.1 second after the original sound. With sound speed at 344 m/s (at room temperature), the total distance traveled must be at least 34.4 meters, meaning the reflector should be at least 17.2 meters away.

Multiple choice

The walls of the halls built for music concerts should

  1. amplify sound

  2. reflect sound

  3. transmit sound

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

Concert hall walls should absorb sound to prevent excessive reverberation and echoes that would muddy the sound quality. Sound absorption creates better acoustic clarity by reducing reflections and preventing sound from bouncing around too much.

Multiple choice

What are ultrasonic waves?

  1. Sound waves having frequency less than the audio frequency range.

  2. Sound waves produced in vacuum.

  3. Sound waves having frequency higher than audio frequency range.

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

Ultrasonic waves are sound waves with frequencies above the upper limit of human hearing (typically >20 kHz). Option A incorrectly describes frequencies below the audio range, and sound cannot propagate in vacuum (eliminating B). C correctly states that ultrasonic waves have higher frequencies than the audible range.

Multiple choice

Sonar makes use of

  1. infrasonic sound

  2. ultrasound

  3. ordinary sound

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

SONAR (Sound Navigation and Ranging) technology utilizes ultrasonic waves for underwater detection and distance measurement. Infrasonic waves are below human hearing range, ordinary sound lacks the precision and directionality needed for SONAR applications, and light is unrelated to acoustic ranging systems.

Multiple choice

What is the requirement for reflection of sound wave?

  1. The size of the reflecting surface must be bigger than the wavelength.

  2. The size of the reflecting surface must be smaller than the wavelength.

  3. The size of the reflecting surface must be equal to the wavelength.

  4. The reflecting surface should be smooth and shiny.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For sound waves to reflect effectively, the reflecting surface must be larger than the wavelength of the sound wave. If the surface is smaller than the wavelength, the sound will diffract around it rather than reflect. Surface smoothness affects reflection quality but isn't the fundamental requirement.

Multiple choice

What are the properties of ultrasound that makes it useful?

  1. High power and high speed

  2. High frequency and high speed

  3. High frequency and bending around the objects

  4. High power and good directivity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ultrasound is useful primarily because it has high power (can penetrate materials effectively) and good directivity (can be focused into narrow beams). High frequency alone doesn't confer utility, and ultrasound doesn't bend around objects - it travels in straight lines due to its short wavelength.

Multiple choice

Find the appropriate word and fill blank (i).

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.

Our ear collects the sound from the surroundings. Pinna or the ____(i)_____ ear receives the signal and passes it through the auditory _____(ii)_______. When the sound wave reaches the eardrum or tympanic _______(iii)______, the pressure on the outside of the membrane increases and forces the eardrum inward. It leads to vibration of the eardrum. The middle ear transmits pressure _______(iv)______ received from the sound wave to the inner ear through three small bones called ear ossicles.

  1. internal

  2. external

  3. artificial

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

The pinna is the visible, outer part of the ear that collects sound waves. It's anatomically known as the 'external ear' because it's the portion located on the outside of the head. The passage describes how sound is collected from the environment and directed inward, making 'external' the logical choice for describing the pinna's location.

Multiple choice

Find the appropriate word and fill blank (ii).

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.

Our ear collects the sound from the surroundings. Pinna or the ____(i)_____ ear receives the signal and passes it through the auditory _____(ii)_______. When the sound wave reaches the eardrum or tympanic _______(iii)______, the pressure on the outside of the membrane increases and forces the eardrum inward. It leads to vibration of the eardrum. The middle ear transmits pressure _______(iv)______ received from the sound wave to the inner ear through three small bones called ear ossicles.

  1. trench

  2. canal

  3. way

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

The auditory canal is the tube-like passage connecting the outer ear to the eardrum. Sound travels from the pinna through this canal to reach the tympanic membrane. 'Canal' is the correct anatomical term for this passage, while 'trench,' 'way,' and 'gutter' are either not anatomical terms or too informal.

Multiple choice

Find the appropriate word and fill blank (iii).

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.

Our ear collects the sound from the surroundings. Pinna or the ____(i)_____ ear receives the signal and passes it through the auditory _____(ii)_______. When the sound wave reaches the eardrum or tympanic _______(iii)______, the pressure on the outside of the membrane increases and forces the eardrum inward. It leads to vibration of the eardrum. The middle ear transmits pressure _______(iv)______ received from the sound wave to the inner ear through three small bones called ear ossicles.

  1. membrane

  2. casing

  3. film

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

Membrane is a tissue; crust is outer layer or surface.

Multiple choice

Find the appropriate word and fill blank (iv).

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.

Our ear collects the sound from the surroundings. Pinna or the ____(i)_____ ear receives the signal and passes it through the auditory _____(ii)_______. When the sound wave reaches the eardrum or tympanic _______(iii)______, the pressure on the outside of the membrane increases and forces the eardrum inward. It leads to vibration of the eardrum. The middle ear transmits pressure _______(iv)______ received from the sound wave to the inner ear through three small bones called ear ossicles.

  1. waves

  2. mutations

  3. tactics

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

Mutation is a change arising from within, which is not applicable in this case.

Multiple choice

Consider the following statements:

  1. In vacuum, sound travels with the maximum speed.
  2. SONAR device uses infrasonic waves to measure the distance, direction and speed of underwater objects.
  3. In dark night, bats use ultrasonic waves to search the prey.

Which of the given statements is/are incorrect?

  1. Only (1)

  2. Only (2)

  3. Only (1) & (2)

  4. Only (1) & (3)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(I) Statement (1) is wrong. Sound needs a medium to travel like air, water, steel, etc. It cannot travel through vacuum.

(II) Statement (2) is wrong. SONAR device uses ultrasonic waves to measure the distance, direction and speed of underwater objects. The frequency of ultra sonic waves is more than 20 khz (more than audible range), which are detected by some special sensors. (III) Statement (3) is correct. Bats emit ultrasonic waves, which are reflected by the prey and then detected by them.

Multiple choice

Which of the following statements is/are correct for sound? (1) Sound is produced whenever a body vibrates in a medium. (2) The speed of sound is affected by the change in pressure.

  1. Only (1)

  2. Only (2)

  3. Both (1) & (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement (1) is correct. Whenever vibrations are produced in any medium (gas, liquid or solid), they arise sound. Statement (2) is incorrect. The sound pressure and the air pressure do not affect the speed of sound. There is a small dependence on humidity, due to the change in average air density, but by far the largest dependence is on temperature.

Multiple choice

Consider the following statements:

  1. The astronaut cannot hear the sound on the surface of moon.
  2. Acoustics is the discipline of sound, which deals with the study of sound and vibrations in liquids. Which of the given statements is/are correct?

  1. Only (1)

  2. Only (2)

  3. Both (1) & (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  1. Statement (1) is correct. Astronaut cannot hear the sound on the surface of moon because sound needs medium to travel, which is absent on moon.
    1. Statement (2) is wrong. Acoustics is the discipline of sound, which deals with the study of sound and vibrations in gases, liquids and solids.