An acoustic energy-based, non-contact or contact testing approach provides low cost, highly accurate, and reliable information to (a) identify flaws and anomalies and (b) assess the integrity of a particular material. This approach is not hindered by surface conditions or impediments, and indeed, looks beneath the surface of the material by propagating an acoustic wave through the material using two differential transducers. A dynamic differential measurement is made of the material under a load condition and an unloaded condition that allows identification and assessment of various characteristics of the material. Multiple "windows" of information may be generated that permit (a) direct detection of flaws, defects, and anomalies using a scattering technique, (b) detection of crack closure and opening used to assess the stability of the material, (c) determination of strain on the material which relates to its performance, and (d) determination of defect dynamics linked to the defect size and stability.