The Pressure Acoustics, Time Explicit Interface has the following domain and boundary conditions listed in alphabetic order, available from the Physics ribbon toolbar (Windows users), Physics context menu (Mac or Linux users), or right-click to access the context menu (all users). Continuity in velocity and pressure is the default condition on interior boundaries. If a boundary separates two different materials the Material Discontinuity or Continuity (the pair version of material discontinuity) condition has to be applied to ensure the continuity in velocity and pressure.