Non-Reflective and Highly Dissipative Acoustic Metamaterials

In this paper, we consider a composite embedded in a homogenous medium and present a method to design the composite’s microstructure so that when it is subjected to an incident acoustic wave, it does not reflect the incoming wave and also dissipates most of it. High dissipation is achieved through a metamaterial design which is naturally characterized by internal resonance. The effective impedance of the metamaterial is evaluated through dynamic homogenization technique and it is used to design a quarter wave transformer to enforce zero reflection at the interface between the metamaterial composite and its surrounding medium. Transfer matrix method is used to calculate the reflection/transmission spectra at the above mentioned interface. Results show that the reflection at the interface is close to zero at the designed frequency and a large fraction of the wave energy which is transmitted across the interface is attenuated.