How this calculator works
A simple energy absorption coefficient is the fraction of incident intensity that is absorbed. For a room, multiply each surface area by its own coefficient, then add the contributions. Divide by total area to obtain an area-weighted mean. The tool uses coefficients from zero to one. Some reverberation-chamber measurements exceed one because of edge effects; those apparent values do not fit this simple fraction model.
Formula
alpha = Iabsorbed/Iincident. Equivalent absorption A = sum(S_i alpha_i); mean alpha = A/sum(S_i).
Worked example
Absorbing 3 W/m2 from an incident 10 W/m2 gives alpha = 0.3. Areas of 10 m2 at 0.2 and 20 m2 at 0.5 contribute 2 + 10 = 12 m2, averaging 0.4.
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Frequently asked questions
Can I average coefficients without areas?
Only when all areas are equal. Otherwise the mean must be weighted by area.
Are intensities areas?
No. Intensity is power per unit area in W/m2; equivalent absorption is expressed in m2.
Where do material coefficients come from?
Use laboratory or manufacturer data for the frequency, thickness and mounting arrangement being modelled.