ok, i hope i've got the right section with this...
basically trying to work with Sabine's equation to calculate RT60 in my living room (it's an assignment, i know it's an otherwise pointless exercise!). i've measured out all of the surfaces and gotten hold of coefficients from the SAE website, but i'm not sure i'm working it out right in the spreadsheet i have built;
take the average of each coefficient in a given octave band, then use this number as ? in the following:
where V is total room volume and S is total area of all surfaces. Now, i don't think this is right at all, but it's how i've seen other people work it out.
multiply each material's total surface area by the coefficient for its given octave band to get the 'open window area' for that material. sum all of these for each octave band and use the following:
RT60=(0.161*V)/(?open window area)
I've now confused myself by reading different takes on using the formulas from about seven different sources, so i'd really appreciate someone else's input!
thanks guys (spreadsheet attached if anyone wants to take a look)