The Pressure Acoustics, Boundary Mode (acbm) interface (), found under the Acoustics>Pressure Acoustics branch () when adding a physics interface, is used to compute and identify propagating and nonpropagating modes in waveguides and ducts by performing a boundary mode analysis on a given boundary. The study is useful, for example, when specifying sources at inlets or analyzing transverse acoustic modes in ducts. It is available for 3D and 2D axisymmetric component models.

When this physics interface is added, these default nodes are also added to the Model Builder: Pressure Acoustics Model, Sound Hard Boundary (Wall), and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions and sources. You can also right-click Pressure Acoustics, Boundary Mode to select physics features from the context menu.

The Label is the default physics interface name.

The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first physics interface in the model) is acbm.

See the settings for Sound Pressure Level Settings for the Pressure Acoustics, Frequency Domain interface.

This physics interface defines one dependent variable (field), the Pressure p. The name can be changed but the names of fields and dependent variables must be unique within a model.