The interpretation of light scattering spectra in disordered solids is from many aspects, an incompletely solved problem, expecially when it is desired to extract from the spectra information about the dynamics of the particles of the system. In this paper, we outline a formalism that can be easily applied to disordered molecular solids, and which can be extensively used in several other cases, even for some liquid samples when certain conditions are satisfied. This formalism is then applied to two particular cases of partially disordered crystals: α-AgI and Ice Ih. In both cases the relation between Raman scattering lineshapes and the densities of vibrational states is clarified; acoustic and optic phonon densities of states are derived and compared with neutron scattering experiments. The results are encouraging and suggest further applications of the formalism.
