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. The time domain version of the background acoustics field feature does not include the plane wave option available fore the frequency domain interface.