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 communication system commonly used terms in electronic communication system elements of communication system electromagnetic waves and communication system

The range of frequency of audio signal is __________.

  1. $20 Hz$ to $20 MHz$
  2. $0$ to $2 kHz$
  3. $20 Hz$ to $20 kHz$
  4. $20 kHz$ to $200 kHz$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The generally accepted standard range of audible frequencies is $20 Hz$ to $20,000 Hz$, although the range of frequencies individuals hear is greatly influenced by environmental factor. Frequencies below $20 Hz$ are generally felt rather than heard, assuming the amplitude of the vibration is great enough. Frequencies above $20,000 Hz$ ($20 kHz$) frequencies are the first to be affected by hearing loss due to age and prolonged exposure to very loud noises.

Multiple choice maths direct proportion and inverse proportion inverse proportion rule of three types of proportions

A stone is dropped into a well and the report of the stone striking the bottom is heard $7.7$ seconds after it is dropped. Assume that the stone falls $16t^2m$ in t seconds and that the velocity of sound is $1,120$  per second. The depth of the well is:

  1. $784$m
  2. $342$m
  3. $1568$m
  4. $156.8$m

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

Since the distance d travelled by the stone and the sound is the same,

 $d = r _1t _1 = r _2t _2$.
 $\therefore$ The times of travel are inversely proportional to the rates of fail: 
$r _1/r _2 = t _2/t _1$,
$\therefore \dfrac{16t^2/t}{1120} = \dfrac{7.7-t}{t}; $
 $\therefore t = 7 (seconds);$
$ \therefore 16t^2 = 16\times 7^2 = 784 (metre)$.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

The term channel is used to indicate

  1. the amplitude range allocated to a given source

  2. the frequency range allocated to a given source

  3. the voltage-range allocated to a given source

  4. all of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Channel represents the different frequency ranges over with radio frequencies exist. A change in channel for device would mean a change in range of frequency over which the device is being operated.

Multiple choice physics world of sounds sound produced by humans propagation of sound production and propagation of sound

Which of the following voices is likely to have minimum frequency?

  1. Baby girl

  2. Baby boy

  3. A man

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

A man’s sound is of the lower pitch as compared to the other options. And we know that pitch is directly proportional to the frequency of sound. So, the frequency of man’s voice will be the minimum among all the options.

Multiple choice physics world of sounds sound produced by humans propagation of sound production and propagation of sound

The voices of men, women and children are different due to difference in:

  1. larynx

  2. lungs

  3. vocal coards

  4. wind pipe
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Larynx is responsible for production of sound , and vocal chords are placed inside the larynx , which are responsible for shrill and grave sound , that makes the sound of a lady shrill and of a man , grave .

Lungs filters the oxygen from air .
Wind pipe is the path of air towards the lungs .

Multiple choice physics world of sounds sound produced by humans propagation of sound production and propagation of sound

On what does the quality of voice depend ?

  1. Thickness of vocal chords

  2. Length of local chords

  3. Stiffness of vocal chords

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The quality of voice depends on the length, thickness and stiffness of the vocal chords. Tight, thin and short vocal chords produce high pitched voice like that of females. Loose, thick and long vocal chords produce low - pitched voice like that of men.

Multiple choice physics world of sounds sound produced by humans propagation of sound production and propagation of sound

With the length of vocal chord, voice quality

  1. changes

  2. remains same

  3. may or may not change

  4. remains same but loudness changes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The voice quality changes as per the length of the vocal chords. Men have about 20 mm long vocal chords, whereas women have about 15 mm long vocal chords. Children have very short vocal chords. That attributes to the different voices of men, women and children.

Multiple choice physics world of sounds sound produced by humans propagation of sound production and propagation of sound

How does sound is 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 voice box or larynx. It is the upper part of the windpipe. 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 world of sounds sound produced by humans propagation of sound production and propagation of sound

The sound waves which cannot be heard by a human ear are called.

  1. Ultrasonic sounds

  2. Infrasonic sounds

  3. Extraordinary sounds

  4. Both (a) and (c)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Human ear has a hearing range of 20Hz to 20KHz.

Ultrasonic and Extraordinary sounds are out of this range but infrasonic sound is near to 20 Hz and can be heard by humans but with difficulty.

Multiple choice physics world of sounds sound produced by humans propagation of sound production and propagation of sound

When we hear a sound, we can identify it source from

  1. The frequency of the sound

  2. The amplitude of the sound

  3. The wavelength of the sound

  4. The overtones present in the sound
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Frequency of the sound is the characteristic of sound waves that helps us to distinguish between two different sounds. For example, sound produced by man generally have low frequency (i.e. low pitch) whereas that produced by woman have higher frequency (i.e. sharp tone). Thus we can distinguish between two sounds by hearing the frequency (pitch).

Multiple choice physics free, damped and forced oscillations forced vibration forced vibrations free, forced and damped oscillations

Frequency of oscillation of a body is $6\;Hz$ when force $F _1$ is applied and $8\;Hz$ when $F _2$ is applied. If both forces $F _1\;&\;F _2$ are applied together then, the frequency of oscillation is :

  1. $14\;Hz$
  2. $2\;Hz$
  3. $10\;Hz$
  4. $10\surd{2}\;Hz$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to question,

$F _1=-K _1\,x\;\&\;F _2=-K _2\,x$

So $n _1=\displaystyle\frac{1}{2\pi}\sqrt{\displaystyle\frac{K _1}{m}}=6\;Hz;$

$n _2=\displaystyle\frac{1}{2\pi}\sqrt{\displaystyle\frac{K _2}{m}}=8\;Hz$

Now $F=F _1+F _2=-(K _1+K _2)x$

Therefore $n=\displaystyle\frac{1}{2\pi}\sqrt{\displaystyle\frac{K _1+K _2}{m}}$

$\Rightarrow n=\displaystyle\frac{1}{2\pi}\sqrt{\displaystyle\frac{4\pi^2\,n^2 _1\,m+4\pi^2\,n^2 _2\,m}{m}}$$=\sqrt{n _1^2+n _2^2}=\sqrt{8^2+6^2}$

$=10\;Hz$