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 economics fundamental concepts and terminologies savings, investment, wealth, welfare and business cycle fundamental duties and directive principles fundamental duties and directive principles of state policy

__________ are of regular nature and repeat themselves after a fixed interval of time.

  1. Periodic variations

  2. Oscillatory variations

  3. (a) or (b)

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

Periodic variations occur after a fixed interval or period of time. They happen repeatedly. In economics, periodic variations can be found in production and consumption.

Multiple choice evs - i communication and mass media understanding communication and impact of mass media satellites in communication importance of transport system artificial satellite

The frequency of transmission of a ratio station is $30\, MHz$. The wavelength of the waves transmitted by the centre will be- 

  1. $5$ meter
  2. $10$ meter
  3. $15$ meter
  4. $20$ meter
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The wavelength lambda is calculated using the formula lambda = c / f, where c is the speed of light (3 * 10^8 m/s) and f is the frequency (30 MHz = 30 * 10^6 Hz). Thus, lambda = (3 * 10^8) / (3 * 10^7) = 10 meters.

Multiple choice record management and office equipment business office - meaning, importance, functions and departments office management business organisation business studies office circulars concept of office management

_______ is a communication instrument that produces sound at a distance by means of electricity.

  1. Internet

  2. Telephone

  3. Fax

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

The telephone is the classic communication instrument designed to transmit sound over distances using electrical signals.

Multiple choice zoology option a: neurobiology and behaviour structure and function of ear perception of stimuli neural control and coordination

The human ear is equipped to register sounds of frequencies between

  1. 20 to 20,000 cycles per second

  2. 1000 to 2000 cycles per second

  3. 5000 to 7000 cycles per second

  4. 5000 to 10,000 cycles per second

  5. 10,000 to 20,000 cycles per second
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The middle ear is mainly known as a sound amplifier of the ear. It has ear ossicles to amplify the sound. The human ear can respond to minute pressure vibrations in the air if they are in the audible frequency range of 20 Hz - 20,000 Hz or cycles per second.

So, the correct answer is option A.

Multiple choice zoology option a: neurobiology and behaviour structure and function of ear perception of stimuli neural control and coordination

Our ear can hear the frequency of sound waves

  1. 20 to 20,000 cycles / sec

  2. 1000 to 2000 cycles / sec

  3. 5000 to 7000 cycles / sec

  4. 5000 to 10,000 cycles / sec
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hearing range describes the range of sound wave frequencies, that can be heard by humans or other animals. Human audible range is commonly 20 to 20,000 Hz. 

Multiple choice zoology option a: neurobiology and behaviour structure and function of ear perception of stimuli neural control and coordination

Rats can perceive sound waves of frequency from ........... KHz.

  1. 20 - 30

  2. 150

  3. 1000

  4. 20 - 90
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The hearing is a mechanism which requires a sound under a particular range of frequency. It is known as the audible range. Ultrasonic sound is the sound of higher frequency and infrasonic are the sound of lower frequency as compared to normal audible range. Rats hearing frequency can be as low as 20 kHz to as high as 90kHz.

So, the correct answer is option D.

Multiple choice physics superposition of waves-1: interference and beats distinction between interference and beats beats and its applications beats in sound waves

Two sound sources are moving in opposite direction with velocity $v _1$ and $v _2$ $(v _1>v _2)$. Both are moving away from a stationary observer.the frequency of both the source is $900\ Hz$. What is the value of $v _1 - v _2 $  so that the beat frequency observed will be $6\ Hz$  ?


Speed of sound =$300\ ms^{-1}$

  1. $1\ ms^{-1}$
  2. $4\ ms^{-1}$
  3. $3\ ms^{-1}$
  4. $2\ ms^{-1}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$f _1 = 900(\dfrac{300}{300+v _1})$

$\implies f _1= 900(1+ \dfrac{v _1}{300})^{-1}$
$\implies f _1 = 900 - 3v _1$
Similarly 
$f _2 = 900 - 3v _2$
So,
$f _1 -f _2 = 6$
$3(v _1 - v _2)= 6$
$\implies v _1 - v _2 = 2\ ms^{-1}$

Multiple choice physics superposition of waves-1: interference and beats distinction between interference and beats beats and its applications beats in sound waves

A sources of sonic oscillations with frequency n= $1700$ Hz and a receiver are located on the same normal to a wall. Both the source and receiver are stationary, and the wall recedes from the source with velocity u= $6.0$ cm/s. Find the beat frequency registred by the receiver. The velocity of sound is equal to $v= 340$ m/s.

  1. $0.2$ Hz
  2. $0.3$ Hz
  3. $0.4$ Hz
  4. $0.6$ Hz
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The wall acts as a moving reflector. The frequency of the sound reflected by the wall is f' = f * (v + u) / (v - u). The beat frequency is the difference between the reflected frequency and the source frequency, which simplifies to f_beat = f * (2u / (v - u)). Plugging in f=1700, u=0.06 m/s, and v=340 m/s gives 1700 * (0.12 / 339.94), which is approximately 0.6 Hz.

Multiple choice physics superposition of waves-1: interference and beats distinction between interference and beats beats and its applications beats in sound waves

Two sound sources (of same frequency ) are placed at distance of 100 meter. An observer, when moving between both sources, hears 44 beats per second. The distance between sound source is now changed to 400 meter then the beats/second heard by observer will be  :

  1. 2

  2. 4

  3. 8

  4. 16
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice physics superposition of waves-1: interference and beats distinction between interference and beats beats and its applications beats in sound waves

Two open organ pipes 80 and 81 cm long found to give 26 beats in 10 sec, when each is sounding its fundamental note. Then the velocity of sound in air is

  1. 337 $m s ^ { - 1 }$
  2. 370 $m s ^ { - 1 }$
  3. 345 $m s ^ { - 1 }$
  4. 350 $m s ^ { - 1 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The beat frequency is 26 beats / 10 sec = 2.6 Hz. For an open pipe, f = v / (2L). The difference in frequencies is f1 - f2 = (v/2) * (1/L1 - 1/L2) = 2.6. Substituting L1 = 0.80 m and L2 = 0.81 m, we get (v/2) * (0.01 / (0.80 * 0.81)) = 2.6, which solves to v = 336.96 m/s, approximately 337 m/s.

Multiple choice physics superposition of waves-1: interference and beats distinction between interference and beats beats and its applications beats in sound waves

Two sound waves with wavelength $5$m and $5.5$ m respectively. each propoggate in a gas with velocity $300$ m/s. we expect the following number of beats per second

  1. 12

  2. 0

  3. 1

  4. 6
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Frequency f = v / lambda. f1 = 300 / 5 = 60 Hz. f2 = 300 / 5.5 = 54.54 Hz. The beat frequency is |f1 - f2| = |60 - 54.54| = 5.46 Hz, which is approximately 6 Hz.

Multiple choice physics superposition of waves-1: interference and beats distinction between interference and beats beats and its applications beats in sound waves

A body is walking away from a wall towards an observe at a speed of 1 m/s and blows a whistle whose frequency is 680 Hz. The number of beats heard by the observe per second is approximately.(velocity of sound in air = 340 m/s)

  1. 4

  2. 8

  3. 2

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

The sound reflects off the wall. The wall acts as a source moving toward the observer at 1 m/s. The frequency heard is f' = f * (v + u) / (v - u). With f = 680, v = 340, u = 1, f' = 680 * (341 / 339) = 684 Hz. The beat frequency is f' - f = 684 - 680 = 4 Hz.