Doping of a Plate-Type Acoustic Metamaterial
Résumé
A periodic arrangement of thin elastic plates ? Plate type Acoustic Metamaterial (PAM) ? has been shown to behave as a Density Near Zero (DNZ) metamaterial. The effective dynamic zero mass density is obtained from the strong dispersion around the band gap associated with the resonance of the plate. Three distinct frequencies can be used to characterize the entire system: the impedance matching frequency corresponding to the resonance frequency of the plate, the frequency at which exact zero effective density occurs, and the frequency of the zero-phase propagation. As a result, the non-delayed propagation, lying in the band gap, always occurs with an impedance mismatch for conventional PAM. Here we propose to acoustically dope the system, by adding one or more designed scatterers, to turn the DNZ metamaterial into a metamaterial with a near-zero effective density and compressibility, a DCNZ metamaterial. In doing so, the frequency offset between impedance matching, zero-phase, and zero density frequencies can be deleted, allowing a zero-phase propagation with quasi-unitary transmission.