a self - contained room capable of shielding the interior environment from magnetic and radio frequency interferences , as well as other wave and vibrational disturbances , comprised of an outer enclosure and an inner enclosure , raised above an existing floor by a fiberglass dowel system . the walls of both enclosures are made of mumetel sheets , pressure sealed to protect against ambient and man - made interferences , with an underlying aluminum structural frame . all seams and penetrations are shielded against wave interferences of natural or man - made origin .