Absorption Needed for a Target RT60
The inverse of the room-acoustics tile: the total absorption a room needs to hit a target RT60, A_required = 0.049 x volume / RT60_target sabins, plus the additional treatment to add over the room's current absorption. A 5,000 ft^3 room targeting 0.6 s RT60 needs 408 sabins; with 250 sabins already, add 158 sabins of treatment (about 200 ft^2 of a panel at coefficient 0.8). Sizes the absorption, not the axial modes (geometry sets those). The acoustician and the venue govern.
Formula and source
A_required = 0.049 x V / RT60_target (sabins); A_additional = max(0, A_required - A_existing).
W.C. Sabine reverberation equation (public domain) solved for the required absorption, the inverse of the room-acoustics tile.
Audience
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