The Acoustics Module includes several predefined multiphysics interfaces. When these interfaces are selected from the Model Wizard or the Add Physics window both contributing physics and the multiphysics couplings are added to the Model Builder. It is always possible to build a model sequentially adding one physics at the time and then coupling them. Note that far from all possible couplings are represented in the predefined physics interfaces. All the couplings are listed in the Coupling Features section.

When physics interfaces are added using the predefined multiphysics interfaces, for example Thermoviscous Acoustic-Structure Interaction, the Selection of the coupling feature, in this case the Thermoviscous Acoustic-Structure Boundary, is automatically set to All boundaries. In this way the multiphysics coupling is automatically active on all boundaries with Thermoviscous Acoustics on one side and Solid Mechanics on the other.

If physics interfaces are added one at a time, followed by the coupling features, the selections are not automatically set. For example, if the single interfaces are added, COMSOL Multiphysics adds an empty Multiphysics Couplings node. You can choose the available coupling features, but you need manually to select on which boundaries they need to be applied, or select All boundaries to recover the predefined behavior.

Another option is to create the coupled predefined multiphysics interface by adding it from the Add Multiphysics window after adding the separate physics interfaces.