How to Calculate Sound Reverberation
Reverberation is the persistence of a sound after the original sound ceases. This is most noticeable in an enclosed area where the echoes of a sound can be heard after the source stops. Reverberation is an essential design consideration in buildings that have specific acoustical requirements such as auditoriums and concert halls. The reverberation of a room depends on its volume, surface area and the acoustical qualities of the surface.
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Instructions
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Determine the reverberation of a room. The most common measure of reverberation is the time it takes for the echoes of a direct sound to drop by 60 dB. This is generally the decrease in sound required to become inaudible to humans.
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Define the reverberation mathematically. The Sabine equation gives the reverberation as RT60 = cV/Sa, where RT60 is the reverberation, c is about 0.161 seconds per meter, V is the volume of the room, S is the surface area of the room and a is the average absorption coefficient of the room.
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Measure the absorption coefficient of the room. The absorption coefficient is the fraction of sound that is absorbed by the room. An open window that doesn't reflect any sound would therefore have an absorption coefficient of 1, and a room that reflects sound perfectly would have an absorption coefficient of 0.
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Record the reverberation time. Make a loud noise (greater than 60 dB) and record the time required for the sound level of the echoes to decrease by 60 dB. This can be done with a recorder that plots the sound level on graph paper, and there are also sound meters that perform this measurement automatically.
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Record the reverberation of different types of noises. Impulsive noise is a sudden noise of very short duration, such as a balloon pop or blank pistol shot. Reverberation can also measure the response time of random noise, such as white or pink noise.
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