Numerical investigation of the potential of tailored inclusions as noise reduction measures

The reduction of noise and vibrations is an important task in automotive and aircraft industry. Various applications require slender or adjustable reduction measures. Metamaterials formed by a periodic assembly of unit cells consisting of non-homogeneous material decomposition and having topology dependent favorable absorption properties can meet this need. The absorption efficiency of different types of metamaterials has already been proven by various authors. Thereby metamaterials formed by a periodic assembly of tuned mass dampers on plate-like structures or porous layers with rigid inclusions have been investigated. Beyond that, we suggest to design metamaterials consisting of inclusions containing appropriately tuned mass dampers embedded in a material layer and to examine their noise reduction potential. It is investigated, whether besides absorbing energy by exciting the damping device, the orientation of the tuned mass damper is active by purposefully deflecting waves inside the structure. The analysis is carried out applying the Wave Finite Element Method. Using the inverse approach of the Wave Finite Element Method, stop bands, i.e. frequencies for which no free wave propagation is observed, are detected. In a parameter study, the influence of the characteristics of the inclusion on the absorption behavior of the metamaterial is determined.