Are shielding properties of the cavity readable in histograms of electric field amplitudes: to scale or not to scale histograms?

Electric field amplitude histograms are generated in solving Maxwell´s equations inside a rectangular enclosure. The histograms are formed from numerical solutions but they are found to be uncorrelated with attenuation properties i.e. the shielding effectiveness of the enclosure. Modifications to the histograms are introduced and whether the modified histograms are more usable to observe important quantities related to shielding properties than original histograms is explored. A simple rectangular enclosure comprising one aperture is studied as an example. The resonant frequencies are calculated and the shielding effectiveness determined. An input of 290 frequencies is selected and corresponding histograms are obtained, ordered according to square-sum differences between selected reference histogram and histograms under considerations. The reference histograms are aimed to correspond to good shielding such that the ordering would be comparable with shielding properties. Modified histograms are found to correspond better with shielding properties than unmodified histograms.