The Acoustic Diffusion Equation (ade) interface (), found under the Acoustics > Geometrical Acoustics subbranch (), solves a diffusion equation for the acoustic energy density. This type of analysis also known as energy finite elements or EFEM. It is applicable for high-frequency acoustics inside coupled rooms when the acoustic fields are diffuse. The interface only exists in 3D. The diffusion of the acoustic energy density depends on the mean free acoustic path and thus on the individual room geometry. Absorption may be applied at walls and a transmission loss may be applied when coupling rooms together. Increased diffusion due to room fitting can be added. Material properties and sources may be specified in frequency bands.

When this physics interface is added, these default nodes are also added to the Model Builder — Acoustic Diffusion Model, Room, and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Acoustic Diffusion Equation 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 ade.

See Sound Pressure Level Settings for the Pressure Acoustics, Frequency Domain interface. Note that only Use reference pressure for air or User-defined reference pressure are available selections.

This section cannot be edited when the Band Input Type is Flat (continuous). For all other options under Band Input Type, the default Nstudy (dimensionless) is 1, meaning that material and other properties defined in the first band are used. To sweep the bands enter a parameter (defined under Global Definitions > Parameters) and solve the model using a parametric sweep in the study, in this way solving the model for the desired number of bands.

Select a Type — Flat (continuous) (the default), Octave bands, 1/3 octave bands, or User defined bands. The frequency content of a model solved using the acoustic diffusion equation all lies implicitly in material parameters, absorption properties, sources and so forth. These can be given in a broadband (or for a single frequency) by selecting Flat (continuous) or in bands when given in this way.

From the list select the element order for the Sound energy density, the default is Quadratic.

This physics interface defines one dependent variable (field), the Sound energy density w. If required, edit the name, which changes both the field name and the dependent variable name. If the new field name coincides with the name of another pressure field in the model, the interfaces share degrees of freedom and dependent variable name. The new field name must not coincide with the name of a field of another type, or with a component name belonging to some other field.