How porosity can reduce the sound radiation of electrical coils?

High-power electrical coils used in the electricity transmission network can create a noise nuisance for local residents. These industrial coils are made up of a multi-strand cable winding, giving them a cylindrical shell shape. Electromagnetic excitation by Lorentz forces induces coil vibration, creating an undesirable sound field. In this study, we investigate analytically and by numerical simulation the reduction of acoustic radiation using regularly spaced apertures. As the shell becomes porous (with a porosity of less than 10%), acoustic short-circuits appear. We show a reduction in radiation efficiency and the impact of apertures on the structure vibration. Our results offer insights into the design and optimization of apertured electrical coils to mitigate noise generation.