The research is concerned with the properties of acoustic phonons in thin films. This knowledge is essential for the unambiguous interpretation of non-equilibrium measurements of these systems. The objective is to obtain a more complete knowledge of phonon dimensionality, occupation number, and transmission between dissimilar solids. The experimental techniques to be employed combine magnetoresistance and electron heating experiments with phonon spectroscopy in the study of novel structures in which the phonon properties can be modified in situ. The research will also be broadened to the investigation of acoutic attenuation in disordered metal films. Films with contacts and connections for precision resistivity measurements will be fabricated inside novel acoutic cavities permitting the simultaneous measurement of sound attenuation and electrical properties.