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

Two identical wires are stretched by the same tension of $101$ N & each emits a note of frequency $202$ Hz. If the tension in one wire is increased by $1N$ , then the beat frequency is:

  1. $2 Hz$
  2. $\frac{1}{2}Hz$
  3. $1 Hz$

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

Frequency f is proportional to sqrt(T). f1 = 202 Hz at T1 = 101 N. New tension T2 = 102 N. f2 = f1 * sqrt(T2 / T1) = 202 * sqrt(102 / 101) = 202 * sqrt(1 + 1/101) approx 202 * (1 + 1/202) = 202 + 1 = 203 Hz. Beat frequency = 203 - 202 = 1 Hz.

Multiple choice modelling gases - the kinetic model ideal gases kinetic theory of gases physics

The pressure of air increases by $100mm$ of Hg and the temperature decreases by $1^0C$. The change in the speed of sound in air at STP is

  1. $61ms^{-1}$
  2. $61mms^{-1}$
  3. $61 cms^{-1}$
  4. $0.61 cms^{-1}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Speed of sound v = sqrt(gamma * P / rho). Since P/rho is constant for an ideal gas at constant temperature, speed is independent of pressure. The change in speed depends only on temperature change: dv/dT = v / (2T). For air at 273K, v = 332 m/s. dv = (332 / (2 * 273)) * (-1) = -0.61 m/s = -61 cm/s. The magnitude is 61 cm/s.

Multiple choice physics stationary waves formation of stationary waves stationary waves and its graphical representation standing waves in strings from moving to stationary stationary (or standing) waves

The frequency of a sound wave is 250 Hz and its wavelength is 100 cm. The distance travelled by a sound wave in the time taken to produce 100 waves is ________.

  1. 100m

  2. 200m

  3. 300m

  4. 400m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$v = 250 \times 1 = 250  m  s^{-1}$
$t = \displaystyle \frac{100}{250} s = 0.45$
Distance travelled by wave in the time taken to produce 100 waves $=$ v $\times$ time
$= $ 250 $\times$ 0.45
$=112.5m \approx 100m$

Multiple choice physics stationary waves formation of stationary waves stationary waves and its graphical representation standing waves in strings from moving to stationary stationary (or standing) waves

Standing waves are produced in $10m$ long stretched wire. If wire vibrates in five segments and wave velocity is $20m/s$, then the frequency is $(in\ Hz)$

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

For a wire of length L vibrating in n segments, L = n * lambda / 2. Here L = 10m, n = 5, so 10 = 5 * lambda / 2, lambda = 4m. Frequency f = v / lambda = 20 m/s / 4m = 5 Hz.

Multiple choice biology neural control and coordination structure of muscle skeletal muscles locomotion and movements

Which of the following is called as stimulus?

  1. Light

  2. Temperature

  3. Sound

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • The stimulus(singular) is any change in the organism's internal or external environment that causes the organism to react. It is of two types external and internal.
  • External stimulus is the stimulus that comes outside of the organism. For example, Light stimulus, heat stimulus, chemical stimulus, sound stimulus, etc.
  • The internal stimulus is the stimulus that comes from inside an organism. For example, Hunger, thirst, etc.
  • So, the correct answer is 'All of the above'.
Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which of the following is a characteristic of a buzzer?

  1. It has different mechanism from electric bell.

  2. It has higher frequency of collision of gong and hammer

  3. It uses only AC power supply

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a buzzer, the simplest sort of doorbell, an electromagnet is used to operate a self-interrupting circuit. You can see how this system works in the diagram below. Click and hold the doorbell button to see how the buzzer works. ... This breaks the doorbell circuit, which shuts off the electromagnet.characteristic of a buzzer It has higher frequency of collision of gong and hammer

Multiple choice resonance oscillations physics

A resonance tube is resonated with tuning fork of frequency 256 Hz. If the length of first and second resonating air columns are 32 cm and 100 cm, then end correction will be 

  1. $1 cm$
  2. $2 cm$
  3. $4 cm$
  4. $6 cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a resonance tube, the resonance condition is L + e = (2n-1) * lambda / 4. Using the first two resonances, L1 + e = lambda / 4 and L2 + e = 3 * lambda / 4, we find 2 * (L2 - L1) = lambda. Substituting the values, lambda = 2 * (100 - 32) = 136 cm, so L1 + e = 136 / 4 = 34 cm; thus, e = 34 - 32 = 2 cm.

Multiple choice resonance oscillations physics

Which of the following is an example of acoustic resonance?

  1. Feedback in guitars

  2. A pendulum

  3. Nuclear magnetic resonance

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

$Answer:-$ A

Acoustic resonance is a phenomenon that consists of a given acoustic system amplifying a sound whose frequency matches one of its own natural frequencies of vibration (its resonance frequencies).
The resonance of a tube of air is related to the length of the tube, its shape, and whether it has closed or open ends. Musically useful tube shapes are conical and cylindrical . A pipe that is closed at one end is said to be stopped while an open pipe is open at both ends. Modern orchestral flutes behave as open cylindrical pipes; clarinets and lip-reed instruments (brass instruments) behave as closed cylindrical pipes; and saxophones, bassoons as closed conical pipes. Vibrating air columns also have resonances at harmonics, like strings (in guitars).

Multiple choice resonance oscillations physics

Pushing a person in a swing is a common example of which type of resonance?

  1. Mechanical resonance

  2. Acoustic resonance

  3. Tidal resonance

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

When we push a person in a swing, we generally match the time between two consecutive pushes, with the time, in which swing comes back to its extreme position. In fact we match our pushing frequency with the frequency of swing to get large arc of swing (amplitude), this is a common example of mechanical resonance.

Multiple choice resonance oscillations physics

A cylindrical tube,open at one end and closed at the other,is acoustic unison with an external source of frequency held at the open end of the tube, in its fundamental note. Then:

  1. The displacement wave from the source gets reflected with a phase change of $ \pi $ at the closed end

  2. The pressure wave from the source get reflected without a phase change at the closed end

  3. The wave reflected from the closed end again gets reflected at the open end

  4. The wave reflected from the closed end does not suffer reflection at the open end
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A cylindrical tube,open at one end and closed at the other,is acoustic unison with an external source of frequency held at the open end of the tube, in its fundamental note, then the displacement wave from the source gets reflected with a phase change of  $\pi $ at the closed end.

so the correct option is A.

Multiple choice resonance oscillations physics

For a certain organ pipe open at both ends, the successive resonance frequencies are obtained at $510, 680$ and $850\ Hz$. The velocity of sound in air is $340\ m/s$. The length of the pipe must be:

  1. $2\ m$
  2. $0.5\ m$
  3. $m$
  4. $0.25\ m$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice resonance oscillations physics

Suggest one way by which rattling sound could be stopped.

  1. Rattling sound can be stopped by changing the speed of the vehicle.

  2. Rattling sound can be stopped by changing the frequency of the vehicle.

  3. Rattling sound can be stopped by changing the vibration of the vehicle.

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

The cause of rattling sound is resonance and it can be stopped by changing the speed of the vehicle.