Abstract: Lightweight sandwich structures have been increasingly used in a wide range of engineering applications (e.g., automobiles, express trains, ship/submarine hulls and aircraft fuselages), and hence their vibroacoustic characteristics are of paramount importance for interior noise reduction. In the pursuit of vibration and noise reduction in civil and military applications, this dissertation deals with the vibroacoustic problems of lightweight sandwich structures immersed in either static or convected fluid. Specifically, structural wave and sound wave propagation as well as dynamic responses and vibroacoustic performances of these structures are systematically investigated by incorporating theoretical modeling, experimental measurement and numerical simulation. An integrated optimal algorithm toward lightweight, high stiffness and superior sound insulation capability is subsequently proposed, based on which preliminary optimal design of prototype sandwich structures is performed. The contents and contributions of the dissertation are summarized in the full text.