The Sound Hard Boundary (Wall) adds a boundary condition for a sound hard boundary or wall, which is a boundary at which the normal component of the acceleration (and thus the velocity) is zero:

For zero dipole domain source (qd = 0) and constant fluid density ρc, this means that the normal derivative of the pressure is zero at the boundary

Sound-hard boundaries are available for all study types. Note that mathematically this condition is identical to the Symmetry condition.