Acoustic Simulation with SimScale — Explained
Natural frequency analysis is one of the most useful applications in FEA. Used especially in relation to modal analysis in structural mechanics, acoustic simulation based on natural frequency analysis for complex geometries can provide essential information about the free vibration of an object or the acoustic behavior of a structure.
What is Acoustic Simulation?
The mathematical basis of modal analysis in Acoustics is eigensystem algorithms, which allow the physical interpretation of the corresponding mode shapes offered by eigenvalues (characteristic values) associated as scalars with an eigenvector (characteristic vector of a square matrix). In many structural analyses, the only desired modes are the lowest natural frequencies.
In a simplified definition, the modal analysis can be described in comparison with frequency analysis, where a complex signal is resolved into a set of simple waves with individual frequency and amplitude parameters. In modal analysis, a complex deflection pattern (of a vibrating structure) is resolved into a set of simple mode shapes with individual frequency and damping parameters .
For many reasons, vibration analysis of mechanical structures represents a very important subject for modal analysis, with eigenvalues being related here to the natural frequencies (eigenfrequencies) of vibration and eigenvectors being the shapes of vibration modes.
The most important applications of modal analyses are related to computer simulations. In mechanical engineering simulation, a good approximation model of the natural frequency behavior is critical in best performance analysis of any prototype project related to a component, product ensemble, or mechanical structure. Different simulation scenarios allow modelling of the vibration response of the structure to multiple excitation forces applied.
Iterative simulation could offer to engineers alternative answers related to model behavior after every physical modification of modal parameters (such as geometry, mass dampers, materials, or stiffness). The predicted response converted in noise, strain, or fatigue effects could be compared with standards and design criteria, leading to improvements for reaching the desired model.
Better understanding of natural vibration modes and predicting possible failure modes using simulation are essential for an effective product manufacturing workflow, reducing costs associated with physical model testing, improving the quality of the product and reducing the time of access to the market.
Acoustics Analysis with SimScale
The SimScale 3D simulation platform is a web-based environment providing powerful end-to-end simulation solutions for a whole set of engineering analyses like Structural Mechanics, Fluid Dynamics, Thermodynamics, Acoustics, and Discrete Particle analysis. Structural Mechanics simulations performed with SimScale are based on a comprehensive set of static and dynamic analysis capabilities for investigating Structural Mechanics phenomena, including also Acoustic Simulation based on acoustic eigenfrequency analysis.
The Finite Element-based solver integrated by SimScale offers the possibilities for multiple natural frequency analysis of complex geometries. The visual images of eigenmodes and eigenfrequencies provide optimum models related to the acoustic behavior of a structure.
Acoustic Simulation in Automotive
Automotive is one of the industries where the modal and frequency analysis is used to determine the acoustic and vibration influence on the associated structures.
An example is the acoustic simulation of a car cabin (image below). This simulation is showing the acoustic eigenfrequencies of a car cabin and the corresponding bounding box and can be downloaded as public template from the SimScale Public Projects.
Want to learn more about simulation with SimScale? Download this booklet.
 Ole Døssing– “Structural Testing, Part II: Modal Analysis and Simulation”, Brüel & Kjær, 1988.