Architectural Acoustics

The science of “Architectural Acoustics” deals with the behaviour of sound within an enclosed space and planning of a building with a view to obtain optimum acoustic effect on the audience.

In 1911, at Harward University in the newly constructed auditorium where a sound uttered by a speaker persisted for a period of 5.5 seconds which resulted in the speech becoming unintelligible to the audience. Professor Sabine who faced with the problem of bad acoustics in a newly constructed auditorium found solutions. Prof. Sabine is regarded as the Father of architectural acoustics.

The following are the various requirements of a good auditorium.

The sound should be intelligible in every part of the hall.
The successive sounds spoken must not overlap.
No echoes and echelon effect should be present so that the quality of sound remain unchanged.
The successive syllables spoken should be clear and distinct without any echo.
Interference and resonance should not be present.
There should be no noise.

Reverberation

When a sound is produced inside the hall, it stays there for some time, even after the sound source is cut-off.
The sound produced by the source reaches the listener a number of times, once directly and successively after reflections from walls, ceiling, floor, chairs etc. Thus ,the listener receives the sound of diminishing intensity because a part of sound energy is absorbed at each reflection.
This prolonged reflection of sound from the ceiling, walls, floor, and chairs etc., is called reverberation.
It is defined as the persistence of sound even after the sound source is cut-off.

Reverberation Time

It is defined as the time taken by the sound wave to fall below the minimum audibility measured from the instant (i.e., from the maximum) when the source has stopped sounding.