Development of a numerical prediction tool for optimisation of apertures, screens and absorbers in partial enclosures around noise sources

Research Project, 2011 – 2015

Noise sources are often partly enclosed to reduce the radiated and transmitted noise. A descriptive example is the engine bay around the engine in a vehicle. The enclosures have apertures to allow for cooling airflow and are densely packed with numerous objects such as cables, pipes, and containers. The enclosures of today are rudimentary and sub-optimal due to lack of fast yet accurate prediction tools for noise radiated through the complex geometry. Classical finite element or boundary element methods are no realistic alternative in the mid- and high-frequency ranges, where computational effort is immense and the results are hypersensitive to small variations in geometry, boundary conditions, and environmental conditions. Therefore, methods based on spatial, frequency and ensemble averages of energetic variables have been developed. The intensity potential approach is such method which is based on the Helmholtz decomposition of the vector field of time-averaged sound intensity and results in a Poisson equation for a scalar intensity potential. In the planned project, the theory of the method is expanded to include the effect of interior objects causing scattering and a boundary condition for absorbers including the directivity of the incident sound. This makes essential development of the intensity potential approach and results in a numerical prediction tool that allows for optimisation of apertures, screens and absorbers in enclosures around noise sources in general.