An Application of Acoustic Metamaterial for Reducing Noise Transfer through Car Body Panels

This paper presents the design of an additional structure based on acoustic metamaterial (AMM) for the reduction of vibro-acoustic transfer function of a car body panel. As vehicles are lighter and those engine forces are bigger recently, it has become more difficult to reduce the vibration and noise transfer through body panels by using just conventional NVH countermeasures. In this research, a new approach based on AMM is tried to reduce the vibration and noise transfer of a firewall panel. First, a unit cell structure based on the locally resonant metamaterial is devised and the unit cell’s design variables are studied to increase the wave attenuation in the stop band of a dispersion curve, where the Floquet-Bloch theorem is used to estimate the dispersion curve of a two-dimensional periodic structure. Also, the vibration transfer and the vibro-acoustic transfer are predicted in a FE model of meta-plate which is composed of a periodic system of the devised unit cell. Next, the driving point mobility of a meta-plate is tested and its design is updated for the better performance in a vehicle. Finally, the revised structures which are mounted on a firewall are tested to verify the vibration transfer and vibro-acoustic transfer characteristics in the firewall. As a result, it is shown that the suggested meta-plate structure has a good effect on reducing the noise transfer through car body panels.