Mid-frequency vibro-acoustic modelling: challenges and potential solutions

At present, the main numerical modelling techniques for acoustic and (coupled) vibro-acoustic analysis are based on element based techniques, such as the finite element and boundary element method. Due to the huge computational efforts, the use of these deterministic techniques is practically restricted to lowfrequency applications. For high-frequency modelling, some alternative, probabilistic techniques such as SEA have been developed. However, there is still a wide mid-frequency range, for which no adequate and mature prediction techniques are available at the moment. In this frequency range, the computational efforts of conventional element based techniques become prohibitively large, while the basic assumptions of the probabilistic techniques are not yet valid. In recent years, a vast amount of research has been initiated in a quest for an adequate solution for the current mid-frequency problem. This paper discusses the various methodologies that are being explored in this perspective. The main focus of this paper lies on the methodology that looks for deterministic techniques with an enhanced convergence rate and computational efficiency compared to the conventional element based methods in order to shift the practical frequency limitation towards the mid-frequency range. In this respect, special attention is paid to the wave based prediction technique for (coupled) vibro-acoustic analysis that is being developed at the KULeuven Noise and Vibration Research group. The method is based on an indirect Trefftz approach. Various recent validations have revealed the beneficial convergence rate of this novel technique, thereby exhibiting its potential to comply with the mid-frequency modelling challenge.