Active Feedback Control on Sound Radiation of Elastic Wave Metamaterials

Abstract

To show the effects of active feedback control on elastic wave metamaterials, this research is focused on effective mass density and sound radiation by a point force excitation. The expressions of effective mass density and sound-pressure level (SPL) are derived. The elastic wave metamaterials consist of double plates that are attached by the four-link mechanisms. To form the four-link mechanisms, the periodic structures consist of the lateral local resonators and the vertical resonator that is bonded by the active feedback control system. Based on the dynamic effective medium method, the effective mass density is obtained and the acoustic–structural response is presented. With the Fourier transform technique, the SPL of the double-plate model in the far field is shown. Results from a single-plate model with and without the equivalent method are compared. This work shows that the influences of effective mass density and SPL can be tuned by the acceleration and displacement feedback in the active control system. Furthermore, it is found that the acoustic–structural response and SPL can be changed by different active feedback control constants.