The room is anechoic and insulated. Anechoic means that the walls are treated to absorb all the sound waves that hit them, and not reflect them back. (Typically, anechoic surfaces are soft and cannot support much weight, so [guess] there is probably a support system to put weight bearing platforms inside.) Insulated means that sounds from outside the room are not transmitted in. A lot of concrete can take care of the high frequencies, but low frequencies often require special suspensions to keep sounds from the earth out.

The most interesting thing is the measured extent of what they've produced.