Abstract
Hybrid or electric automobiles which is environmentally-friendly has been becoming obtaining. In these automobiles, noise induced by an engine is decreased, but road noise has relatively come to stand out. Damping sheet and sound-proof materials are widely used in multi-layered structures to suppress vibration and noise in automobiles. The number of combinations of multi-layered structures are too enormous to calculate all possible combinations. Therefore, this paper calculates efficiently for lighter and better sound proofing multi-layered structures than existing multi-layered structures. Finite element method that has already verified the accuracy quantitatively with the experimental results is used to calculate vibration, but it takes a very long time to calculate the analysis result. We employ transfer matrix method that is shorter time than finite element method. In transfer matrix method, multi-layered structures are expressed by transfer matrix using Biot's model to analyze efficiently. Lighter and better sound proofing efficiency multi-layered structures were efficiently calculated by using a multi-objective genetic algorithm having four objective functions that are mass per unit area, sound pressure level, transmissivity and absorption coefficient.
