3. Attenuation measurements for shielded loudspeakers and shielded cables

3.1 How electromagnetic fields penetrate shielded enclosures

Consider a shielded enclosure consisting of a parallelepiped with metal walls made of a highly electrically conductive material such as copper. When the six walls of the enclosure form ideal junctions with no contact resistances and no openings, however tiny, the enclosure constitutes a shield with high electromagnetic immunity. In this case, when subjected to an incident electromagnetic plane wave, the attenuation generated by the enclosure can exceed 120 dB.

Unlike the infinitely flat shielding model described in the previous steps, it is virtually impossible to calculate the attenuation provided by the metal parallelepiped. Only sophisticated numerical simulations can resolve this difficult question....