The Impedance node can be added as a subfeature to the Acoustic FEM–BEM Boundary coupling. It is used to define an interior impedance between the FEM and the BEM acoustic domains. It can, for example, be used to model a perforated plate between the domains or as a simplified model of a thin elastic layer.

Choose the (interior) Impedance model from the list as User defined (the default), Perforated plate, Thin plate, Membrane, or Porous mass layer. For the details of the settings, see the Interior Impedance/Pair Impedance feature in The Pressure Acoustics, Frequency Domain Interface.