Tag: study of sound

Quizzes (14) Questions (314)

Questions Related to study of sound

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

The time of reverberation of a room A is one second. What will be the time (in seconds) of reverberation of a room, having all the dimensions double of those of room A:

  1. 2

  2. 4
  3. $\frac{1} {2}$

  4. 1
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Time of reverberation $\propto$ $\frac{V} {A}$ (sabine's formula)

Where V = volume of room and A = area of room
Area of new room becomes 4 times of A and Volume becomes 8 times of V
Time of reverberation will be 2 seconds

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

The reverberation time of a theatre is $0.1 sec$. The volume of the other theatre is exactly half. If the total absorption is same then the reverberation time of second one

  1. $5 sec$
  2. $0.5 sec$
  3. $0.05 sec$
  4. $0.005 sec$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sabine formula for reverberation time states that T is directly proportional to the volume V and inversely proportional to total absorption A. Since the volume is halved while total absorption remains the same, the reverberation time is also halved, making it 0.05 seconds.

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

An auditorium of dimensions $(100\times40\times10)\space m^3$ contains $1000\space m^2$ curtains of absorption coefficient $0.2\space m^{-2},\space 2000 m^2$ of carpets of absorption coefficient $0.7\space m^{-2}$. If $1000$ men of absorption coefficients $0.9$ per person are sitting in the hall, then reverberation time is

  1. $2.7\space s$
  2. $7.2\space s$
  3. $3.5\space s$
  4. $3.7\space s$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Volume of the room          $V = 100\times 40 \times 10 = 4\times 10^4      m^3$

Effective surface area of the room           $A = (0.2) 1000  +  (0.7) 2000  +  (0.9) 1000  =  2500$
Now reverberation time       $T _r = 0.161  \dfrac{V}{A}$
$T _r = 0.161  \dfrac{4\times 10^4}{2500} = 2.576    s$

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

A stone is dropped from the top of a tower of $125m$ high into a pond which is at base of the tower. When will the splash be heard at the top? (Given $g = 10ms^{-1}$ and speed of sound $=340ms^{-1}.$)

  1. $5s$
  2. $0.36s$
  3. $5.36s$
  4. $2s$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Time to fall: h = 0.5 * g * t^2 -> 125 = 5 * t^2 -> t^2 = 25 -> t = 5s. Time for sound to travel up: t2 = h / v = 125 / 340 = 0.367s. Total time = 5 + 0.367 = 5.367s.

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

When all of the audience come out of the audotirium the reverberation time became$\frac{4}{3}$ of that when packed with the audience. If all $400$ persons come out, the ratio of the absorption of the auditorium to that a person is 

  1. $1600$
  2. $1200$
  3. $3000$
  4. $1000$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

T = k * V / A. T_empty = k * V / A_auditorium. T_full = k * V / (A_auditorium + 400 * A_person). Given T_empty = 4/3 * T_full. So (A_auditorium + 400 * A_person) / A_auditorium = 4/3. 1 + 400 * A_p / A_a = 1.333. 400 * A_p / A_a = 0.333. A_a / A_p = 400 / 0.333 = 1200.

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

The reverberation time of a hall of volume $200m^{-3}$ is $1.7s$. The reverberation time if $20$ persons having absorptions $0.4$ entered the hall, nearly is 

  1. $1.5s$
  2. $1.4s$
  3. $1.3s$`
  4. $1.2s$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

T1 = 0.161 * V / A1 = 1.7. A1 = 0.161 * 200 / 1.7 = 18.94. New absorption A2 = A1 + 20 * 0.4 = 18.94 + 8 = 26.94. T2 = 0.161 * 200 / 26.94 = 1.195s, which is approx 1.2s.

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

A stone is dropped into a lake from a tower 500 metre high. The sound of the splash will be heard by the man approximately after

  1. 11.5 seconds

  2. 21 seconds

  3. 10 seconds

  4. 14 seconds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fall time: 500 = 5 * t^2 -> t^2 = 100 -> t = 10s. Sound time: 500 / 340 = 1.47s. Total time = 11.47s, approx 11.5s.

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

Fill in the blank.

___________ is created when a sound or signal is reflected causing a large number of reflections to build up and then decay as the sound is absorbed by the surfaces of objects in the space.

  1. Reverbaration

  2. Echo

  3. Response

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

A reverberation, or reverb, is created when a sound or signal is reflected causing a large number of reflections to build up and then decay as the sound is absorbed by the surfaces of objects in the space which could include furniture and people, and air.