Reverberation Time in "dead" Rooms
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چکیده
culation by the aid of a reliable formula, then, is an important aspect of applied acoustics. A reverberation time formula enables one to calculate the reverberation time once the volume, surface area and average absorption coefficient of the surface of the room are known; or if the reverberation time is measured it enables one to calculate the average coefficient of absorption of the surface treatment. A correct reverberation time formula is, therefore, much to be desired. Theories of reverberation leading to Sabine's reverberation time equation have been given by W. C. Sabine (1900), • Franklin (1903)? Jaeger (1911), a Buckingham (1925). 4 Recently Schuster and Waetzmann (1929)* have pointed out that Sabine's formula is essentially a "live" room formula and they have shown as we also show that the reverberation time equation varies somewhat with the shape of the room. The present paper presents an analysis based on the assumption that image sources may replace the walls of a room in calculating the rate of decay of sound intensity after the sound source is cut off, which gives a form of reverberation time equation more general than Sabine's; it points out the difference between the basic assumptions leading to the two types of formulae; it adds experimental data which support the more general type; and it ends with the conclusion that no one formula without modification is essentially all inclusive.
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