Numerical modelling of acoustic metamaterial made of periodic Helmholtz resonator containing a damping material in the cavity

Acoustic metamaterials are frequently used in many fields such as aerospace, buildings and ground transportation industries for low frequency noise control applications. Different solutions based on membrane or Helmholtz resonators have been investigated in the past few years. In the present study, a numerical design of acoustic metamaterial made of Helmholtz resonator with a membrane in its cavity is presented. The resonator with a neck extended into the cavity is periodically embedded within a porous material. The membrane inside the resonator cavity is modelled as a linear isotropic elastic material with free and fixed boundary conditions. The transmission loss (TL) of the proposed metamaterial design, predicted by finite element method presents multiple resonant peaks while only one peak is obtained with a conventional resonator. Two TL resonance peaks are observed when the membrane circumferential boundary is free inside the resonator cavity. For fixed boundary conditions, more than two resonance peaks are obtained. The proposed metamaterial design can therefore be used in many industrial applications for low frequency noise attenuation.