Physics · Science General

Acoustics and Sound Waves

2,006 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 audible, infra and ultra sound with its application study of sound physics

Which of the following statement is/are true in case of waves ?

  1. Transverse vibrations are set on the string of a guitar.
  2. As compared to light, a sound wave produced on the moon will take a time about $10^6$ times longer to reach the earth.

  3. A sound note of wavelength 1 cm in air cannot be heard by a man.

  4. Sound travels faster in water than in air.
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

(A) When a guitar string is struck , string is disturbed and the medium (string) particles vibrate perpendicular to the direction of motion disturbance , therefore transverse vibrations are set on the guitar string . -True

(B) Sound wave are longitudinal mechanical waves , which require a medium to travel as there is no medium on moon , so they cannot travel there and can't reach to earth . Whereas light waves ,being electromagnetic waves can travel to earth . -False
(C) If wavelength $\lambda=1cm=0.001m$ and $v=332m/s$ ,
then frequency $f=v/\lambda=332/0.001=332000Hz$ ,
that is an ultrasonic frequency which cannot be heard by a man . -True
(D) Sound travels faster in liquid than gases due to higher elasticity of liquids , therefore sound travels faster in water than in air .  -True

Multiple choice audible, infra and ultra sound with its application study of sound physics

Most students have an audible range of about 50Hz to 50kHz.

  1. True

  2. False

  3. Ambiguous

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

Answer is B.

The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors. Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. Frequencies above 20,000 Hz can sometimes be sensed by young people. High frequencies are the first to be affected by hearing loss due to age and/or prolonged exposure to very loud noises.
Hence, the statement is false.

Multiple choice audible, infra and ultra sound with its application study of sound physics

Human ears can sense sound waves travelling in air having wavelength of ________.

  1. ${10}^{-3}m$
  2. ${10}^{-2}m$
  3. $1 m$
  4. ${10}^{2}m$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Human ears can sense sound waves travelling in air whose frequencies $f$ lie in the range of $20Hz$ to $20kHz$

The average speed $v$ of sound in air is $335m/s$
Wavelength $\lambda=\cfrac vf$
Hence the wavelength range of audible sounds is $\cfrac{335}{20000}$  $to$  $\cfrac{335}{20}$
That is $1.675\times{10^{-2}}$ metres to $16.75$ metres
You can see that among all the 4 options given, only $1m$ fits in the audible range.

Multiple choice audible, infra and ultra sound with its application study of sound physics

Voices of men, Women and children different because of

  1. The pitch

  2. The length and the thickness of vocal cords.

  3. Both

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

The voices of men, women and children differ from each other
due to the following factors:

i) The pitch is one of the most essential factors to determine the voice of the individual. For example, men have lower-pitched voices while women have higher-pitched voices.

(ii) Second factor which brings in the difference in the voices is the length and the thickness of vocal cords.  from each other due to the following factors

Multiple choice audible, infra and ultra sound with its application study of sound physics

 State True or False.

All inaudible sounds produces frequencies less than 20 Hz.

  1. True

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

The frequency range of audible sound is $20 Hz$ to $20000 Hz$. Thus, the sound below the frequency 20 Hz is inaudible for human ear and the sound above the frequency 20000 Hz is inaudible for human ear. Thus, the given statement is false. 

Multiple choice different modes of communication and their uses information technology communication systems physics

The difficulty to recognize the speaker's voice over the telephone is due to poor quality of sound.

  1. True

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

The bandwidth used to transmit telephone signals is very low , it is generally around $4 KHZ$ in range .So, the quality of audio signals is low , therefore make it difficult to recognize the speaker's voice .

In modern day technologies . the bandwidth of the audio signals is however increased to around $9 KHZ$

Multiple choice different modes of communication and their uses information technology communication systems physics

The sound waves in telephonic communication are converted into electric signals by the________ and the signals reach the _____________  at the other end by cables.

  1. mouthpiece,mouthpiece

  2. mouthpiece,earpiece

  3. earpiece,mouthpiece

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

The mouthpiece has a mic that converts the audio waves  from our voice to electric signals , that are carried further away to receiver .

The earpiece has a speaker ,A speaker converts the electric signal received to the audio wave .

Multiple choice different modes of communication and their uses information technology communication systems physics

The part of telephone instrument which is placed in front of mouth and collects sound and then propagates the information in the form of electromagnetic waves is called:

  1. Mouth-piece

  2. Receiver

  3. Cable wire

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The earpiece consists of an internal receiver that translates electronic signals into sound that a person can comprehend. On the other end of the handset is the mouthpiece, which consists of the transmitter. The transmitter is really a microphone that catches sound waves. The sound is then converted.  Hence the answer is mouth-piece.
Multiple choice social studies importance of transport system importance of transportation system introduction to transport and communication transportation services language, writing and great books

The constant sounds of vehicles create ________________.

  1. air pollution

  2. noise pollution

  3. water pollution

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

Noise pollution is caused by the loud and constant sounds generated by engines, horns, and traffic movement in urban areas.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

An ultrasound equipment work at frequency:

  1. Higher than $20,000 Hz $
  2. Higher than $10,000 Hz $
  3. Lower than 4420,000 Hz $
  4. Lower than $10,000 H _2 $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. ultrasound devices operate with frequencies from 20000 Hz up to several gigahertz.

Multiple choice biology animal behaviour ethology natural selection coordination in human beings- chemical control endocrine system in humans

The highest sound frequency which a human being can detect is 20,000 vibrations/second. What is the highest frequency which a bat can detect?

  1. 75,000

  2. 50,000

  3. 10,000

  4. 150,000
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Most bats use frequencies in the range 20-80 kHz, only a few bats use frequencies less than 20 kHz.

So, the correct option is '75,000'.

Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

Heart sound which is longer is

  1. Lubb

  2. Dub

  3. Both are equal

  4. Sometimes (a) and sometimes (b).
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first heart sound, 'Lubb', is caused by the closure of the atrioventricular valves. It is longer and lower in pitch compared to the second heart sound, 'Dub', which is caused by the closure of the semilunar valves.