When running EMC tests (radiated immunity) with automotive components there shall be used hazardous RF fields.
(The radiated power might be >10 kW!).
To protect the operating personel from these fields and also to protect the radio reception near the test facillity, radiated immunity tests need to be done in a shielded enclosure (Faraday cage), i.e. an absorber lined chamber.
This absorber lined chamber is lined with a material, that absorbes electromagnetic waves. Usually these are
used pyramide absorbers and/or ferrite absorbers.
These absorbers minimize the reflection of electromagnetic waves at the walls. So, an absorber lined chamber provides similar conditions for EMC testing like a free space test site.