These are the audio anechoic and resonating chambers of Denmark's Technical University (DTU). The anechoic chambers work in much the same way as the microwave anechoic chamber in my previos post, but the point is to remove reflections of audio waves rather than radio waves. The spikes on the walls, ceilings and floor absorb all sound waves, so there is no echo at all - it's quite strange to stand in the room. There is a net in the middle of the room that acts as the floor, so when you stand in the middle, there is an equal distance to the floor and ceiling, which is also quite strange. The room is used for testing all sorts of audio devices and the amount of noise they make.
The resonating chambers do the exact opposite of the anechoic chambers - they are covered with hard surfaces that are designed to reflect the sound as much as possible.
