Practical High-Frequency Acoustic Simulation with the Actran Radiosity Solver

Predicting noise at high frequencies is a persistent challenge across automotive, aerospace, architectural, and industrial design because the traditional Finite Element Method (FEM) and the Boundary Element Method (BEM) can become computationally expensive as the wavelength decreases and mesh requirements increase.

The Actran radiosity solver provides a much more efficient alternative by modeling acoustic energy rather than resolving acoustic waves. A new white paper explores how the radiosity solver works in depth, but we’ve provided a quick summary here to get you acquainted with how it works.

Why Traditional Methods Struggle

The Finite Element Method (FEM) and Boundary Element Method (BEM) both demand increasingly fine meshes as wavelengths get shorter, driving up computational cost for large models. Ray-based approaches often need many rays to converge. For vehicle cabins, large enclosures, industrial facilities, and environmental noise prediction, none of these options is especially practical.

An Energy-Based Alternative

The Actran radiosity solver takes a different approach. Rather than resolving acoustic waves, it models how acoustic energy is exchanged between surfaces. Originally developed for thermal radiation and later adopted in computer graphics for light energy, radiosity computes the total energy leaving each surface, including both emitted and reflected energy. It assumes surfaces act as diffuse reflectors, an approximation that grows more valid at high frequencies, where multiple reflections and scattering dominate.

Key to the method are view factors, which quantify energy exchange between visible surfaces. Because they depend only on geometry and visibility, they can be precomputed and reused. Actran calculates them on standard graphics hardware, so no specialized HPC accelerators are required.

Because the solver works on acoustic power rather than pressure, no volumetric mesh is needed. External sources can be represented as power inputs, and transmission loss can be assigned to surfaces so reflection, absorption, and transmission are modeled together. The method applies to both interior and exterior propagation.

Engineering Value

With the radiosity solver, model preparation is simpler, requiring only surface discretization and material properties. Solutions often take minutes on a standard workstation rather than hours, which makes high-frequency analysis accessible to both experienced CAE specialists and occasional users. Engineers can evaluate multiple design alternatives and make informed decisions earlier in development.

Use Cases

Vehicle cabin: A door-mounted loudspeaker was modeled as an injected power source. Comparing a uniformly low-absorption cabin to with one with seats showed how localized treatments change energy distribution. The full analysis took less than one minute.

Factory and warehouse: Complex, large-scale geometries can be solved in just a few minutes, supporting occupational noise assessment, layout optimization, and evaluation of acoustic treatments.

Urban noise: A moving source was discretized into 116 load cases, and the contributions were summed into a cumulative noise map. The analysis took about an hour on a standard laptop.

One Part of a Complete Strategy

Radiosity complements FE and BE methods at low frequencies and hybrid approaches in the mid-frequency range. Together, they give Actran coverage across the entire frequency spectrum.

Learn More

The full white paper covers the method's theory, validation results, limitations, and detailed case studies, including figures and results.

Download the complete Actran radiosity solver white paper today to see how the Actran radiosity solver can accelerate your high-frequency acoustic analysis and help your team make better decisions earlier in the design cycle.