Abstract
In this chapter we consider acoustics in composite media with two different components. In the first configuration the composite medium $$Q$$ consists of some elastic body $$\varOmega ^{(s)}$$ and a poroelastic medium $$\varOmega $$ . In the second configuration the composite medium $$Q$$ consists of some liquid domain $$\varOmega ^{(f)}$$ and a poroelastic medium $$\varOmega $$ . And in the second configuration we consider two different poroelastic media $$\varOmega $$ and $$G$$ . For each type of component all the limiting regimes are already known and the main problem here concerns the boundary conditions on the common boundary between the two different components.