Modal quantities and their usage for evaluation of radiated sound power

• Applicant: Professor Dr.-Ing. Steffen Marburg
• Subject Area: Acoustics
• Term: from 2012 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 230029255

Vibrating structures radiate sound. The radiated sound power is a measure to quantify this sound. It is a global quantity, which makes evaluation costly in particular in cases requiring solution over a frequency range. This is a consequence of the fact that system matrices depend implicitly upon frequency in most formulations for the exterior acoustic problem. Therefore, modal methods similar to solution of the interior acoustic problem are hardly used in these cases. There are two types of modes in external acoustics. These are the frequency depending radiation modes and frequency independent normal modes. Both of them are well suited as basis functions for reconstruction of the radiated sound power. However, similarities and differences of these modes are barely studied and, thus, hardly known. It is just clear that both are well suited to be used for analysis over frequency ranges and for application in structural-acoustic optimization if structural parameters are controlled and the fluid geometry remains unchanged. The project will start with a working package to provide tools for evaluation of frequency depending radiation modes and frequency independent normal modes. The second step includes a more detailed investigation of normal modes understand their nature with respect to physics. It is expected that the results of the second step allow to understand similarities and differences of both types of modes. Crucial part of the project consists in finding criteria to categorize frequency independent normal modes into modes to be relevant or not relevant for evaluation of the radiated sound power. Knowledge about the modes being relevant for the radiated sound power can be valuable for modal superposition over a frequency range and in structural-acoustic optimization.

• DFG Programme: Research Grants