On the time and geometry independence of elastodynamic spectral energy density

It is shown that the acoustic spectral energy density E(ω) deposited by an elastodynamic source is, at times, subsequent to cessation of action of the source, independent of time. It is furthermore shown that, suitably smoothed, E(ω) is independent of the distant geometry of the elastic body in which the source acts and thus that E(ω) may be calculated knowing only the source character and specimen geometry in the vicinity of the source. Inasmuch as the diffuse field assumption allows E(ω) to be estimated from simple measurements of the reverberant field, acoustic emission source character may be extractable from such measurements.