Reverberation - class-IX
Description: reverberation | |
Number of Questions: 59 | |
Created by: Seema Agrawal | |
Tags: study of sound sound waves acoustics wave motion physics |
Why do we hear more clearly in a room with curtains than in a room without curtains?
_________ is a device which is based on multiple reflection and isused for sending amplified sound in a particular direction.
Which of the following device does not work on the multiple reflections of sound waves?
The persistence of audible sound due to the successive reflections from the surrounding objects even after the source has stopped to produce that sound is called
Reverberation time of a hall used for speeches should be very short. Why?
Curved surfaces which are used in big hall to direct the sound waves towards the people sitting in a hall are known as:
Mark the correct statement .
i) rock music also becomes less pleasing with excessive reverberation.
ii) excessive reverberation is desirable in case of orchestral and choral music.
iii) excessive reverberation makes the speech of a person indistinct.
A device based on multiple reflection used as hearing aid.
If the ceiling of a cineural is made flat, what will happen
Identify the device which work on the reflection of light:
Excessive reverberation in any auditorium/hall is not desirable because :
Megaphones or loudhailers, horns, musical instruments such as trumpets and shehnais, are all designed to ______.
Why the ceiling of concert halls, cinema halls made curved?
In an auditorium or big hall excessive reverberation is highly _______.
If the ceiling of a cinema is made flat, what will happen?
Reverberation time of a hall used for speeches should be very short. Otherwise
Why do we hear more clearly in a room with curtains than in a room without curtains?
Mark the correct statement :
Mark the correct match
Identify the device which work on the reflection of sound.
Which of the following are examples of multiple reflections of sound?
What is multiple reflection of sound?
The persistence of audible sound due to the successive reflections from the surrounding objects even after the source has stopped to produce that sound is called _________.
Why do distant sounds such as those of traffic and loudspeakers become louder during the night time than during the day time?
In an unoccupied hall of a choultry you will experience the echo effect of sound. If the same hall is furnished with almirahs, tables, chairs,and other commodities, you may not experience the echo clearly. It is because,
The persistence of sound in a closed enclosure, due to continuous reflections at the walls, even after the source has stopped producing sound is known as
Select the instrument that works on the principle of multiple reflection of sound.
Perforated card boards are used in halls, for
For good absorption of sound in auditorium it requires
In an auditorium the big curtain when falls suddenly then the reverberation time
Which of the following has largest absorption coefficient?
Upholstered seats in cinema halls are arranged for
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
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
In theatres, big halls., the reverberation of sound is a common problem.
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:
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)
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
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:
Standing waves and echoes are based on which acoustic phenomenon?
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
When a source of sound crosses an obsever then change in appearent frequency obseved by the observer is $2$% of its initial frequency. If the speed of sound is $350 m/s$ then be-
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
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 $=340ms^{-1}.$)
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
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
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
Fill in the blank.
The walls and ceiling of an auditorium are covered with a fibrous material to
What will happen if the reverberation time in a big hall is too long?
A man standing between two cliffs hears the first echo of a sound after 2 sec and the second echo 3 sec after the initial sound. If the speed of sound be $330 {m}/{sec}$ the distance between the two cliffs should be
(1) The reflected pulse will be in same orientation of incident pulse due to a phase change of $\pi$ radians.
(2) During reflection the wall exerts a force on string in upward direction.
For the above given two statements choose the correct option given below.
(A). The reverberation time is dependent on the shape of the enclosure, position of the sources and observer.
(B) The unit of absorption coefficient in S.I. system in metric is sabine
A hall has volume 4x6x10 m$^3$. If the total sound absorption of the hall is 27.2metric sabine and 40 visitors are in the hall and each is equivalent to 0.5metric sabine sound absorption then the reverberation time is
The reverberation time of a room is t seconds. Another room of double the dimensions with the walls of the same absorption coefficient will have a reverberation time :
The ratio of the absorption of an auditorium to that of a person is 1000. If 500 persons are accommodated in that auditorium then the ratio of the reverberation times with and without
audience is:
The reverberation times in a cinema theatre are 3s, 2s when it is empty, filled with audience respectively. The reverberation time when the theatre is half filled with audience is
A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fire a gun simultaneously. He hears echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340 $ms^{-1}$, find the distance between the cliff and the observer :
The term reverberation time is generally understood to be the reverberation time at which of the following frequencies?