reverb time

Ry122

I have some data representing the sound pressure level decay in a room after a loud noise has been shut off. The SPL drop for each octave band is known and I'm just wondering how you would determine the reverberation time from this.

It would involve determining the gradient of the reduction in the SPL and extrapolating this out to determine the time required for a 60dB drop, but I'm just wondering how to determine
the overall reverberation time from each of the octave band sets of data.