Electromagnetic shielding uses a shield made of conductive or magnetic material to hold the electromagnetic field on one side of a boundary, so that the inside and outside of the shielded space do not interfere with each other. It stops outside electromagnetic waves from disturbing precise measurement inside, and it also stops a device’s own emissions from leaking out.
In practice the shielding effectiveness depends on the material, the structure and the quality of the work. The shield has to stay electrically continuous and well grounded, while doors, windows, vents and the points where cables pass through the wall are the parts most likely to leak, so they need dedicated treatment such as contact fingers, waveguide vents and filters. If any one detail is left undone, the overall effectiveness drops sharply.
Electromagnetic shielding is often combined with acoustic treatment and used in test spaces for electronics, telecommunications and automotive electronics. Shielding effectiveness has to be confirmed by professional testing, so the design and build are best handled by a vendor with experience in both acoustic and electromagnetic engineering.