New methods are outlined for dealing with the vibration responses of complex flight vehicle structures to local and to diffuse acoustic excitation. Energy absorption at structural joints and acoustic radiation resistance are shown to be important in establishing levels of these responses. Some experimental results pertaining to energy absorption coefficients and radiation resistance are given, and procedures for estimating the latter are discussed. Feasibility studies of vibration absorbers utilizing viscoelastic spring elements and distributed mass systems and of vibration isolators compose6of viscoelastic leaf springs are summarized. Only the latter are found to possess some practical advantages over conventional systems. The results of experiments are presented which demonstrate that sound-tostructure coupling may be reduced significantly by the use of beams of special design whose stiffness decreases with increasing frequency. An analytical investigation is summarized which shows that generally damping of only the plates summarized which shows that generally damping of only the plates of beam-plate systems may be more desirable than damping of only the beams.