New Functionality in Version 5.2a

Background Acoustic Fields in Thermoviscous Acoustics (Scattered Field Formulation)

The Thermoviscous Acoustics interfaces are now defined in the so-called scattered field formulation. This enables users to add a background acoustic field to a model. The background field can be either User Defined or Plane Wave. The Plane Wave option defines a plane traveling wave with physically consistent viscous and thermal attenuation.

Using this new feature it is possible, for example, to create simple sources when modeling transmission problems where thermal and viscous losses are important or to study scattering of small objects (small as compared to the acoustic boundary layers). As an advanced application example, the feature can be used in conjunction with the Thermoviscous Acoustics, Boundary Model interface to create sources at the inlet of waveguides.

Directivity Plot

The new Directivity plot is a dedicated acoustics plot for the analysis of loudspeakers and other electroacoustic transducers. The plot allows audio engineers to depict the spatial response of a loudspeaker as a function of both frequency and spatial angle in a contour-like plot. Representing the spatial response in this manner is very common in the loudspeaker industry. Measured data is often represented in the same manner. The plot includes many options for formatting to achieve maximal insight into the modeled data. Some of the key formatting features are:

•	Normalization: The input sound pressure level data can be normalized either with respect to a specific polar angle, with respect to the maximal value (at each frequency), or have no normalization.

•	Evaluation: The evaluation circle can be defined at any location in space and it is possible to define a reference direction that sets the 0 deg. direction.

•	Coloring and style: Format the data as filled surfaces, lines, and add labels. It is also simple to switch the layout of the axis and have the frequency on either the x- or y-axis.

Background Acoustic Fields in Linearized Navier-Stokes (Scattered Field Formulation)

The Linearized Navier-Stokes, Frequency Domain interface is now defined in a so-called scattered field formulation. This enables users to add a background acoustic field to a model. The background field can be entered as user-defined expressions for the pressure, acoustic velocity, and temperature variation. This can be an analytical expression defining a certain type of wave, but it can also be the solution of another acoustic model. An applications example could be to create simple sources when modeling transmission problems where thermal and viscous losses are important.

Background Acoustic Fields in Linearized Euler (Scattered Field Formulation)

The Linearized Euler, Frequency Domain interface is now defined in a so-called scattered field formulation. This enables users to add a background acoustic field to a model. The background field can be entered as user-defined expressions for the pressure, acoustic velocity, and temperature variation. This can be an analytical expression defining a certain type of wave, but it can also be the solution of another acoustic model. An applications example could be to create simple sources when modeling transmission problems where thermal and viscous losses are important.

The feature was present in the previous version of the Acoustics Module but the name has been changed from Incident Acoustics Fields to Background Acoustics Fields. The feature has been updated and improved.

Ray Acoustics: Compute Ray Power and Surface Sound Pressure Level (SPL)

New ray power computation functionality has been added to the Ray Acoustics interface. This means that four intensity computation options exist:

•	Compute intensity

•	Compute intensity and power

•	Compute intensity in graded media

•	Compute intensity and power in graded media

The options that existed in version 5.2 have been renamed. Using principal curvatures is now Compute intensity, and Using curvature tensor is now Compute intensity in graded media. Once one of the options that calculate the ray power is selected, it is possible to add a Sound Pressure Level Calculation subnode to the Wall conditions. This new feature sets up a predefined accumulator that calculates the surface sound pressure level, including the effects of surface properties, such as the absorption coefficient. The variables can easily be plotted in postprocessing.

Ray Acoustics: Meshless Ray Tracing

Ray tracing no longer requires a computational domain mesh if the medium has homogeneous properties (nongraded media). In this case, the material parameters can be defined globally. The only requirement is that a model includes at least one boundary condition, such as a wall or material discontinuity. Rays can thus propagate over long distances in geometries that do not need to have their domains meshed. Rays can even be released and propagate outside the geometry. This could be used in underwater acoustics applications or in large concert hall simulations.

Spherical and Cylindrical Waves in Background Pressure Field and Incident Fields for Pressure Acoustics

In the Pressure Acoustics, Frequency Domain interface, the Background Pressure Field and Incident Pressure Field (a subnode to the radiation conditions) features have been extended to include cylindrical and spherical waves. This makes it possible to set up more complex incident or background acoustic field more easily. Fields that are generated by exterior point sources or small vibrating bodies can be approximated by a monopole type source.

Electro-Acoustic Couplings for Loudspeakers

In the AC/DC Module, new features have been added and improved that simplify and extend the electromagnetic couplings in transducers with, for example, coils. This is highly relevant when modeling loudspeaker drivers. The Multi-Turn Coil domain feature now supports the Velocity (Lorentz Terms) in 3D and in 2D axisymmetry. On the structural mechanics side, the Lorentz force contribution can be picked up automatically as a Body Load. This is showcased in the Loudspeaker Driver model in the Application Library.

Logarithmic and ISO Preferred Frequencies Options for defining Frequencies in the Study Settings

Two new entry methods have been added when selecting frequencies in the study:

•	Logarithmic: A start and stop (frequency) and a number of frequencies per decade can be entered (in all products).

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Logarithmic and ISO preferred frequencies: This option is only available with the Acoustics Module and is activated by enabling the Advanced Study Options. For the ISO preferred frequencies, you can select a start and stop frequency and the desired interval (Octave, 1/3 Octave, 1/6 Octave, 1/12 Octave, and 1/24 Octave). The 1/3 octave preferred frequencies are defined based on ISO 266. The standard option is extended to frequencies based on the preferred numbers of ISO 3 (series R20, R40, and R80) to define 1/6 Octave, 1/12 Octave, and 1/24 Octave intervals.

Updates to the Perfectly Matched Layers

For users working with perfectly matched layers (PMLs) that want to perform advanced customization of the layer properties, several options have been added:

•	Enable and disable PMLs in the solver. This is useful if modeling scattering problems where the source is a computed field.

•	User-defined geometry types, which are available if the PML has a nonstandard geometry. This option can also be used if the automatic PML geometry detection fails (for example, for some imported CAD geometries).

•	User-defined coordinate stretching functions for defining the scaling. This allows advanced users to tailor the scaling inside the PML, for example, to very efficiently absorb waves in specific physics configurations.

Other Enhancements and Important Bug Fixes

•	Updated the Far-Field plots with a new option to specify the reference direction that defines the 0-degree angle.

•	A new option to calculate temperature and two new boundary conditions in the Compressible Potential Flow interface.

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Compressible Potential Flow has two new boundary conditions: Interior Wall (Slip Velocity) and Mean Flow Velocity Potential. Moreover, there is now an option to automatically calculate the temperature field in the flow; this option can be used when setting up the background flow for a linearized Potential Flow Model.

•	Two new thermal boundary conditions have also been added to the Thermoviscous Acoustics, Frequency Domain interface:

-	A Heat Flux condition for when a pulsing heat source generates acoustic waves.

-	An Interior Temperature Variation condition for modeling, for example, a thin plate with a harmonic temperature variation possibly generated by resistive heating from a pulsing current.

•	As a consequence of renaming Incident Acoustics Fields to now be called Background Acoustics Fields in the Linearized Euler interfaces, all variables have _i changed to _b.

•	Time derivative variables have changed names in the Linearized Navier-Stokes and Linearized Euler interfaces. Names changed from: p_t to pt, u_t to ut, rho_t to rhot, and T_t to Tt.

•	It is now possible to add two contributing point sources in the Acoustic Diffusion Equation interface.