Optimisation of source arrays for the reproduction of finely resolved inhomogeneous sound fields
This thesis is part of the VIRTECH project funded by the French National Research Agency. The experimental characterization of the vibro-acoustic response of structures excited by random pressure fields is of great interest to industrialists. In the field of transport (automotive, aeronautics, railways, etc.), this type of random excitation is encountered, for example, when a turbulent flow develops in the wall of a moving vehicle. In the building industry, it corresponds to the normative excitation that is the diffuse acoustic field. The characterisation of industrial structures with respect to this type of excitation requires experimental means which can be very expensive (i.e. aerodynamic tuning, flight tests, reverberation chamber) and for which it is difficult to control all the physical parameters (i.e. background noise, temperature, field homogeneity, etc.). The reproducibility of the measurements can then be questioned, which makes it difficult to compare different technological solutions. It is therefore of great interest to have a laboratory tool that allows the reproduction of random excitations in an environment that can be controlled. In this context, techniques have been developed over the last few decades to generate synthesised fields from networks of sources (loudspeakers). These technologies have been experimentally validated for the excitation of flat panels by diffuse and homogeneous acoustic fields. In order to extend the field of application of these techniques, we wish to raise three scientific obstacles: (1) increase the spatial resolution of the synthesised fields to represent the pressure fluctuations induced by a homogeneous turbulent boundary layer; (2) take into account a "source" network geometry that does not conform to the target structure in order to be able to synthesise the fields on non-planar geometries and (3) synthesise spatially inhomogeneous pressure fields to represent cases encountered in practice.
The aim of the thesis is therefore to develop and control a source network for the reproduction of finely resolved inhomogeneous sound fields on a complex geometric structure.
