Acoustic field reconstruction in the presence of masking objects

In acoustics, field reconstruction methods aim at retrieving acoustic fields (pressure, velocity and intensity) from acoustic measurements around a radiating source, which is often a vibrating structure of complex shape (pumps, engines…). If they are extensively used in laboratory conditions, their application to in situ characterization is not straightforward due to the presence of disturbing sources or masking objects, or to non-anechoic environments. The inverse Patch Transfer Function (iPTF) approach, thanks to the concept of virtual acoustic volume modelled by a finite element model, has already demonstrated its ability to deal with sources of complex shape and the presence of disturbing stationary sources in a non-anechoic acoustic environment. The objective of this article is to show how the presence of rigid masking objects can be easily and efficiently taken into account. A numerical experiment consisting of a thin, simply supported rectangular plate radiating noise in a semi-infinite acoustic field and partially masked by a rigid parallelepiped is presented. The acoustic fields identified and the directivity diagrams are compared with the reference and show that iPTF is able to cancel the presence of the masking object even if the latter completely covers the radiating plate. Finally, an industrial example consisting in an electric motor in operation is presented. Two configurations were tested: with and without the presence of a rigid object. Comparison of the results shows that the fields identified are in good agreement, demonstrating the ability of iPTF to cancel out the effect of masking objects.