The Impedance node adds an impedance boundary condition with the option to select between several built-in impedance models and engineering relations. See the Impedance in the The Pressure Acoustics, Frequency Domain Interface.

Note that the Impedance condition contributes with the Wall feature. It specifically inherits the defined Mechanical condition (No slip or Slip (perfect)) and Thermal condition (Isothermal or Adiabatic) from the Wall feature. For specific combinations of mechanical and thermal conditions with the Impedance condition, add a separate Wall feature on the source boundary.