Originally Posted by SAC
And why are you desirous to measure the RT60 of a MODE? If the room continues to be pressurized, the mode will last indefinitely! You need a much bigger computer! ;-))))
That certainly qualifies as a bizarre statement. The rate at which a modal resonance decays is governed by the absorption of the surfaces along the mode's path at its frequency and the length of the path. That rate of decay can be expressed in many ways, but a 60dB decay time is as good as any in an acoustic context.
On the more general point you do come across as someone who has discovered an electric screwdriver and is so in love with it thinks it is the tool for every job. Hammers still have their place.