Surface contributions with respect to acoustic energy quantities applied to cavities

• Applicant: Professor Dr.-Ing. Steffen Marburg
• Subject Area: Acoustics
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 418936727

Interior noise problems in vehicle cavities at low frequencies are usually assessed based on the sound pressure at one or a few field points, e.g. at the driver's ear. This procedure, however, has the drawback that these points may not be chosen representatively and thus, lead to wrong results. Commercial software has been offering an acoustic panel contribution analysis based on the sound pressure at certain points for more than two decades. These surface panel contributions are complex valued and visualized in a bar chart with one value per predefined panel.The situation is different for radiation problems in which the radiated sound power - an energy quantity - accounts for the quantity to be assessed. The surface contributions to the radiated sound power are determined by the acoustic intensity which is a local quantity and which can be, similar to the (complex valued) surface contributions to the sound pressure, positive and negative. Hence, the acoustic short circuit may still remain in the data and thus, not clearly allowing to identify regions of large contributions to the radiated sound power. In recent years, the applicant has developed a technique which can visualize surface contributions which are free of the acoustic short circuit and just isolate the non-negative surface contributions to the radiated sound power. Later on, Williams has called this resulting quantity as non-negative intensity. It is the aim of the project to develop a method to evaluate non-negative surface contributions with respect to an acoustic energy quantity in cavities. These surface contributions will be be visualized and tested. Then, an efficient method is developed to substitute a surface integral for the volume integral that is originally to be solved for evaluation of the acoustic energy. This will benefit from the analysis based on the boundary element method, even though these surface contributions can also be determined by applying the finite element method. The subsequent working package will reveal similarities of the surface contributions with an efficient sensitivity analysis required in structural optimization for acoustic problems. Here, it will be investigated how to efficiently determining the acoustic energy of a cavity, if, in the process of a structural optimization or an uncertainty analysis, the geometry of the cavity remains constant and the free parameters affect the structural design only. The applicant is assuming that this problem is also closely related to the surface contributions.

• DFG Programme: Research Grants
• International Connection: Australia
• Cooperation Partner: Professorin Nicole Kessissoglou