The above video shows off Logitech's anechoic chamber.

The anechoic chamber does precisely as the name indicates: eliminate echoes. The chamber is built atop a separate foundation from its surrounding office structure, allowing further structural isolation from sound events -- such as from seismic activity -- and accuracy of testing.

To give an idea for the space, the chamber is 35 x 25 x 20 feet (LWH) in dimensions, but the 'user' is suspended on a sort-of pseudo-floor, grounded centrally within that 20 foot height.