Visco-thermal Effects in Acoustic Metamaterials Based on Local Resonances

This chapter is devoted to study the contribution of viscothermal effects in some specific acoustic metamaterials. Particularly, in those whose negative effective parameters are a consequence of embedded resonances in the building units. The chapter briefly reports the different approaches developed in order to study viscothermal losses in environments where their expected contribution is relevant.

The finite element method and the boundary element method (BEM) can be used when explaining the properties of artificial structures with corrugated surfaces where viscothermal losses are relevant, like the ones analyzed here. The BEM is applied to comprehensively study the case of a single‐negative metamaterial.

This quasi‐two‐dimensional metamaterial structure is made of a two‐dimensional waveguide with a square distribution of drilled holes and effectively behaves as a material with negative bulk modulus as the one introduced by Fang et al.