A closed room environment is viewed as a lossy cavity, characterized by possibly a line-of-sight component and diffuse scattering parts from walls and internal obstacles. A theory used in acoustics and reverberation chambers is applied for the electromagnetic case, and main issues related to measurement systems, antennas characteristics, diffuse energy properties, and human exposure are investigated. The goal of this paper aims first toward validation of the assessment of the reverberation time in an environment using a virtual multiple-input-multiple-output channel system. Second, the reverberation time in an adjacent room is investigated, and hence, a measurement-based method is readily developed to assess the absorption cross section and the whole-body specific absorption rate of humans at 2.3 GHz in a realistic closed environment.