Reverberation of (sound) waves is the effect that is caused by multiple reflections (echos) of the waves from walls and obstacles. These cause the effect of persistence of sound for a longer time duration than otherwise. This is a desired effect (to a certain extent) in many cases, but in a controlled way. The huge meeting halls and seminar halls are designed for a good reverberation.
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We can observe this
effect when we are among a lot of tall buildings, among high mountains, or in a
big hall (meeting hall or cinema hall).
We can hear the sound directly coming from the
source and also from the reflections of the sound from nearby tall structures.
The first reflection of sound takes some time. The further reflections of sound
takes lesser and lesser time duration. They also decrease in intensity
too in time.
Reverberation time is the duration for the
reverberation sound to be a millionth of its intensity.
The design of big halls and auditoriums needs to
take care of reverberation effect. Reverberations help the people at different
locations to receive sound at uniform intensity. But we do not want to
have the reverberations to last very long. An optimized value will be chosen.
The wall shapes, ceiling shapes, coating or plastering on walls are done
according to acoustic effects such as reverberation.