Abstract
To analyze vibration transmission between the double walls in cars in the low frequency range, we applied a numerical method previously proposed by the authors. As a model for cars, we deal with mixed structures composed of a porous material sandwiched between a damped steel plate and a cover plate. Especially, we focus on the influences of beads in the damped steel plate on vibration transmission from the steel plate to the cover plate. The porous material on the top of the bead in the steel plate is removed locally corresponding to the height of the bead. Because of short distance between the steel plate and the cover plate in this region, vibration transmission through this region is investigated numerically. In our numerical method, we select displacement vectors as common unknown variable for the mixed structure including porous materials, viscoelastic materials and elastic materials. We solve under coupled condition. Further, explicit expressions of modal loss factor for the mixed structures are derived using asymptotic method. Using this technique, eigenvalue analysis and frequency response analysis are performed.
