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| Acoustics of Buildings |
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| An auditorium is a part of a building in which large number of people may be seated to listen to a speech or music. It is not uncommon to find an auditorium, which may be an architectural masterpiece but falls below standards on acoustic considerations. In spite of the usage of amplifiers, the audience may not be able to hear the speech clearly or may miss many of the tonal qualities present in the music. A lecture hall or a concert hall has to be planned properly so that the sound energy is distributed uniformly over the entire audience without affecting the speech intelligibility and the tonal qualities of music. |
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| An open window is a perfect absorber of sound. It absorbs the entire sound energy incident on it and transfers it to the regions outside the building and reflects none. The situation is quite different when reflecting surfaces, like a case in a concert hall, surrounds a sound source. A sound wave strikes a wall and is reflected back into hall, it propagates across the room until it strikes another surface and is again reflected and so on. |
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| A listener in an enclosure not only receives the sound directly from the source but also reflects sounds, which reach him at different instants of time. Thus, the sound intensity level increases until the listener is immersed in sound, coming from different directions at equilibrium level. Just as sound builds up to an equilibrium level, it decays from an equilibrium level. The sound level trails off exponentially, as the reflected waves become successively weaker. |
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