Vibration and noise level induced by external excitation should be predicted to design configuration of sound-proof media, such as damping sheet and multi-layered sound-absorbing material. On the other hand, the weight must be reduced to improve fuel consumption. Therefore, performance of sound-proof media need to be maximized with a given weight. In our laboratory, a design method to find the optimal layout of sound-absorbing material has been developed in order to minimize sound pressure level inside passener compartment by topology optimization. Material characterization has been also developed by using multi scale analysis to figure out the relationship between micro structures of sound-absorbing material and macroscopic properties such as absorption coefficient.