The theory originally developed by London and Beranek of diffuse source field sound transmission between rooms included both direct and reverberant field contributions in the receiving space. The direct field component was calculated by assuming that a receiver was located near the radiating surface. Since a receiver may not be simultaneously close to all surfaces at once the theory is inconsistent for multiple path transmission. By taking into account the falloff of the direct field's formulation can be determined which allows for both self consistency and an extension of the theory to radiation from buildings to the exterior environment.
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