Analaysis of a loudspeaker

The following example models a loudspeaker that reproduces bass frequencies. A cone-shaped diaphragm is vibrated by virtue of a voice coil. This is in turn affected by an assembly consisting of a toroidal permanent magnet and iron pieces that act together to create a strong radial magnetic field in the gap where the voice coil is located. When an electric signal is applied, the cone starts vibrating, creating sound with the same frequency as the signal.

The study consists of a series of simulations. It starts by calculating the opposing voltage (“back EMF”) that is induced in the voice coil when it moves; and then proceeds to compute the coil’s electrical impedance. The study next feeds this into an analysis of the cone’s structural displacements and acoustic pressure-wave distribution, which is a two-way coupling. The final result of the simulation is the speaker’s sensitivity, 1 m from the source.

Acoustic waves in a car interior

In this model, a point source generates a pressure wave in a testbench car interior. The sound level is measured at another point over a range of frequencies.

The model summarizes the basic steps for modeling a classical acoustics problem:

• Generation of a 3D geometry by extruding from a 2D workplane
• Definition of constants and expressions for future parameter sweeps and analysis
• Definition of subdomain and point settings
• Solving using an iterative solver and preconditioning

Absorptive muffler

The pressure-wave propagation in a muffler is modeled in this example. The model’s purpose is to show how to analyze both inductive and resistive damping in pressure acoustics by comparing the simulation of an empty chamber with one lined with glass wool.

The approach given here is generally applicable to analyzing the damping of propagation of harmonic pressure waves, where the Delany-Bazley model is used.

Aeroacoustics in a torbufan engine

The modeling of aircraft-engine noise is a central problem in the field of computational aeroacoustics. In this example, the harmonically time-varying acoustic field from a turbofan engine under various conditions is simulated. Furthermore, the additional attenuation of the acoustic noise obtained by introducing a liner inside the engine duct is calculated.

Acoustic-structure interaction in a cylinder

Fluid acoustics coupled to structural objects, or acoustic-structure interaction, represents an important application area in many engineering fields.

In the study, the coupled acoustic-structural response of a capped, hollow aluminum cylinder filled with and immersed in water is modeled. The acoustic pressure waves resulting from a line and a point source are investigated and compared.