Interior Sound Hard Boundary (Wall)
The Interior Sound Hard Boundary (Wall) sets up a wall condition on an interior boundary. Add this node from the Interior Conditions submenu. The pressure is discontinuous across this boundary.
When postprocessing and plotting variables on boundaries with interior conditions, the boundary variables (with extension _bnd) give the average value of the two sides. Use the up (_up) and down (_down) variants to depict the values on both sides of the boundary.
See also Postprocessing BEM Results in the Modeling with the Pressure Acoustics Branch (BEM-Based Interface) section.
In the BEM formulation, interior conditions cannot intersect other (exterior) conditions. It is recommended that this type of model is set up by using FEM in the region around the interior condition and BEM outside of that region.