Supplementary material from "Coupling strength assumption in statistical energy analysis"

The examples of coupled oscillators and statistical ensemble of coupled plates excited by broadband random forces are discussed. In each case, a reference calculation is compared to the SEA calculation.

First, it is shown that the main SEA relation, the coupling power proportionality, is always valid for two oscillators irrespective of the coupling strength. But the case of three subsystems, oscillators or ensemble of plates, indicates that the coupling power proportionality fails when the coupling is strong. Strong coupling leads to non-zero indirect coupling loss factors and even sometimes, to a reversal of the energy flow direction from low to high vibrational temperature.