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| Sabine's Formula |
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| Prof. Wallace C. Sabine (1868 - 1919) of Harvard University investigated architectural acoustics scientifically, particularly with reference to reverberation time. He deduced experimentally, that the reverberation time is: |
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 directly proportional to the volume of the hall |
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 inversely proportional to the effective absorbing surface area of the walls and the materials inside the hall |
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| where, V is the volume of the hall, a is the absorption coefficient of an area A. If the volume is measured in cubic feet and area in square feet, then the experimentally obtained value of the constant of proportionality, according to Sabine is 0.05. Then, |
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| If there are different absorbing surfaces of area A1, A2, A3, A4, etc., having absorption coefficients a1, a2, a3, a4 etc., then, |
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| If the area is measured in square meters and the volume in cubic
meters, then Sabine's formula can be written as: |
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| Increasing the effective area of complete absorption like, changing the wall materials or adding more furniture may decrease an excessive reverberation time for a hall. But this also decreases the intensity of a steady tone. Also, too much absorption will make the reverberation time too short and cause the room to sound acoustically 'dead'. Hence, the optimum reverberation time is a compromise between clarity of sound and its intensity. |
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