FE based measures for structure borne sound radiation

The sound emission of thin-walled radiating components is a common objective of structural optimisation. Acoustic measures are not implemented in common FE-codes. Thus, different velocitiy based measures will be compared: the kinetic energy, the equivalent radiated power (ERP) and the lumped parameter model (LPM). The most common approach - The ERP - is based on the sound intensity in normal direction and the sound pressure on the radiating surface. Assuming a unit radiation efficiency all-over the surface and neglecting local effects, this is a common approach for an upper bound of structure borne noise. Therein, the sound power finally results from the squared velocity integrated over the radiating surface and the constant fluid impedance. As ERP usually requires extra post processing to consider the velocity in normal surface direction, the kinetic energy is essential in common FEA results including all velocity components apart from the normal direction, too. Thus, it is less accurate but maybe usable for optimisation abilities. In contrast, LPM is a simplification of the Rayleigh-integral and thus gives quite accurate results but requires significant higher computational costs than ERP. Possibilities and limits of estimating the emitted sound power by these three methods will be shown.