The Acoustic Diffusion Equation interface and eigenvalue study will produce the modes that decay exponentially for each room, including the effect of couplings to adjacent rooms and wall absorption. The modes are of the form

where each mode wi has an associated eigenvalue λi (this is the exponential time scale). The eigenvalue directly gives the reverberation time T60 of that subsystem

A list relating the eigenvalues to the reverberation times is automatically shown in an evaluation group in the Results node. Identify the mode associated with a given reverberation time by looking at the Sound Energy Density Mode default plot.