Studies of spectral analysis of the scattered longitudinal and shear waves from crack-like flaws in solids were carried out in the region of ka ≥ 1. Experimental data are analyzed and compared to two new theories developed recently for elastic wave-diffraction from cracks. These theories relate the amplitude spectra of scattered L and S waves to crack parameters such as size, orientation, surface roughness, etc. On the development of the interpretation obtained from phase spectral information the scattered phase from spherical cavities was calculated from exact theory and compared to experimental data.