Acoustic Test Chambers are echo-free enclosures with a sound energy absorption level of 99% to 100%, or a reflected sound pressure level of 10% or less. The frequency at which the energy absorption drops below 99%, or the pressure reflection exceeds 10%, is known as the low-frequency cut-off.

Sound absorption is obtained by lining the walls, ceilings, and floor with wedges or other sound absorbing elements or SuperSoft panels, depending on performance level required and cut-off desired.