A hybrid method for vibroacoustics based on the radiative energy transfer method

A hybrid method is proposed to predict the noise radiated in the high-frequency range by a structure whose vibratory behavior is rather in the low-frequency range. This problem meets for instance when the structure radiates inside some closed acoustical spaces. The proposed approach is called hybrid as it couples two methods valid on different frequency bands respectively used for the structural and acoustical systems. Low-frequency structural approaches generally provide the velocity field on the vibrating surface while methods adapted to high-frequency acoustical studies are based on energy data: so the main difficulty for the coupling is a problem of data compatibility. In the proposed hybrid method, the radiated noise is predicted by using the radiative energy transfer method which is an energy boundary integral method basically equivalent to the known ray-tracing method for acoustic applications. Adequate equivalent energy sources are estimated on the surface of the vibrating structure from the surface pressure and velocity fields. These sources are then introduced in the integral equation of the radiative energy transfer method. The approach is applied to predict the radiation of a ribbed plate sandwiched between two absorbant panels: good agreement is observed with the results given by the boundary element method. Generally speaking, the hybrid method can be considered to apply the radiative energy transfer method for high-frequency acoustical predictions from the knowledge of the vibratory behavior of a structure.