When the Background Acoustic Fields feature is added to a domain, it is possible to define the value of the background acoustic field variables pb, ub, and Tb. Using this feature, it is possible to set up scattering problems as well as defining acoustic fields at an inlet of a waveguide (using a small domain at the inlet).

Enter expressions for the Background acoustic pressure pb, the Background acoustic velocity ub, and the Background temperature variation Tb. These can be analytical expressions or values of dependent variables solved in a previous study that defines the background field.