Acoustic analysis simulates the generation and propagation properties of either the coupled acoustic fluid-structure interaction (FSI) or the uncoupled pure acoustic wave in the given environment. Support is available for modal, time-harmonic, transient and steady-state acoustic analysis.

The program assumes that only relatively small pressure changes are allowed with respect to the mean pressure. An acoustic analysis usually involves modeling the acoustic phenomena in an acoustic fluid and in a structure. A coupled acoustic-structural interaction analysis solves these equations together: the structural dynamics equation, the linearized Navier-Stokes equations of fluid momentum, and the flow continuity equation. A pure acoustic analysis models the acoustics fluid.

In an acoustic analysis, one of the two following matrix equations is solved. For pure acoustic phenomena, the program solves for this finite element dynamic matrix equation:

where [M_F], [C_F], and [K_F] are the mass, damping, and stiffness matrices, respectively, and {f_F} is the external excitation vector in the acoustic fluid.

In acoustic-structural interaction application, the program solves for the fully coupled finite element dynamic matrix equation:

where [M_S], [C_S], and [K_S] are the mass, damping, and stiffness matrices, respectively, and {f_S} is the external force vector in the structure. [R] is the coupled matrix and represents the coupling conditions on the interface between the acoustic fluid and the structure.

For more information about the matrices, see Derivation of Acoustic Matrices and Acoustic Fluid-Structure Interaction (FSI) in the Mechanical APDL Theory Reference.

In room acoustics, the acoustic energy diffuse equation predicts the sound field distribution and the sound decay in rooms:

For more information about the matrices, see Room Acoustics in the Theory Reference.

The full linear Navier-Stokes equation is solved for acoustic phenomena with viscous and thermal effects in small acoustic devices:

For more information about the matrices, see The Full Linear Navier-Stokes (FLNS) Model in the Theory Reference.

The mixed displacement and pressure formulation is cast to solve the poroelastic acoustic problem. The sound is absorbed in poroelastic media:

For more information about the matrices, see Poroelastic Acoustics in the Theory Reference.