Tag: study of sound

Questions Related to study of sound

For good absorption of sound in auditorium it requires

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. a few windows to be opened

  2. all closed windows

  3. maps hanging from walls

  4. hanging light curtains.

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Correct Option: A
Explanation:

A few window should be kept opened for the good absorption of sound in auditorium. Because if we open few windows, more sound will absorbed and more will be the sound clarity and better sound effect can be experienced. 

In an auditorium the big curtain when falls suddenly then the reverberation time

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. increases

  2. decreases

  3. Remains same

  4. becomes zero

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Correct Option: B
Explanation:

The reverberation time will get decreased because curtain will abrosh the sound and more sound will get abrashed then the earlier.  

Which of the following has largest absorption coefficient?

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. heavy curtain

  2. cork

  3. marble

  4. open window

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Correct Option: D
Explanation:

The absorption coefficient of a body is the ratio of the heat radiation absorbed by the body to the total heat radiation incident on it. Since an open window can allow all the radiation into it, it is a good absorber. Hence its coefficient is highest.

Upholstered seats in cinema halls are arranged for

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. absorption of sound

  2. reflection of sound

  3. diffraction of sound

  4. to hear an echo

Show answer
Correct Option: A
Explanation:

Upholstered seats in cinema halls are arranged for better absorption of sound and to decrease the reverberation time. 

The total absorption of a volume $12000 m^3$ is equal to $1000 m^2$ in the units of an open window. Total absorption of the hall is increased to $2000m^2$ due to entry of audience. The change in its reverberating time is

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. $1s$

  2. $2s$

  3. $3s$

  4. $4s$

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Correct Option: A

The volume of a cinema theatre is 100m x 60m x 20m and total acoustic absorption in it is 6800metric sabine. The reverberation time in that theatre is

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. 1.5 s

  2. 2 s

  3. 3 s

  4. 4 s

Show answer
Correct Option: C
Explanation:

$R.T=\frac{1.61}{10}\times \frac{V}{A}$
=2.84se
=3 sec

In theatres, big halls., the reverberation of sound is a common problem.

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. True

  2. False

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Correct Option: A
Explanation:

since the halls and theatres are big enough so that we can distinguish between the generated sound and the reflected sound so the reverbereation  easily happens .

so the answer is A.

A meeting hall of volume $100\times30\times10 m^3$ has a reverberation time of 3 seconds. If 1000 visitors are in the hall. The absorption of total visitors if the sound absorption of each visitor is 0.5 is:

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. 500metric sabin

  2. 600metric sabin

  3. 700metric sabin

  4. 800metric sabin

Show answer
Correct Option: A
Explanation:

absorption of each visitor is 0.5
so, absorption for 1000 visitor is $1000\times 0.5$
$=500 metric sabine$

A source of sound A emitting waves of frequency 1800 Hz is falling towards ground with a terminal speed v. The observer B on the ground directly beneath the source receives wave of frequency 2150hz. The source A receives waves, reflected from frequency nearly: (Speed of sound = 343 m/s)

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. 2150 Hz

  2. 2500Hz

  3. 1800Hz

  4. 2400Hz

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Correct Option: B
Explanation:
Frequency received by source A is
$f=1800\left( \dfrac { 343+V }{ 343-V }  \right) $
$for\quad V;$
$2150=1800\left( \dfrac { 343 }{ 343-V }  \right) $
$343-V=\dfrac { 1800\times 343 }{ 2150 } $
$V=56\quad m/s$
$\therefore \quad \quad f=1800\left( \dfrac { 399 }{ 287 }  \right) \simeq 2500Hz$

A man standing between two parallel hills, claps his hand and hears successive echoes at regular intervals of $1\ s$. If velocity of sound is $340 \mathrm { ms } ^ { - 1 }$, then the distance between the hill is

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. $100\ m$

  2. $170\ m$

  3. $510\ m$

  4. $340\ m$

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Correct Option: B