I've worked in one of these for a happy summer making measurements of acoustic diffuser panels. I quite enjoyed it. However, it looks that that room actually has a regular floor; mine didn't. You lowered your own suspended floor (metal grill tiles) onto scaffold poles to get into the room, then tore it all up as you left. Falling off the "floor" was a Really Bad Idea; those foam pyramids have got a steel spike up the middle for rigidity, and you'd be in deep trouble if you fell onto them from 6 feet up (especially as no-one was going to hear you scream).
There was a safety microphone wired to the door switch for this reason (which also meant it wasn't QUITE such a good idea to say rude things about people in there :-)
However, it looks that that room actually has a regular floor
Look carefully at the picture, he's not standing on a solid floor, he's standing on a wire frame over more absorbers. Their website has a better pic: http://www.orfieldlabs.com/Researchtour4.html
IOW, their chamber is (fully) anechoic, not just hemi-anechoic.
Yes, you're quite right; I thought that was a particularly ugly patterned carpet he was standing on. I think that says more about British carpets than anything else :)
Looks like their wire floor is a bit more permanent than the design I was using; my microphone was on a rotating boom that could be swept 360 degrees from outside, and my sample mounting was a pole down to the real floor, so we could have the absolute minimum of interference from the mountings.
There was a safety microphone wired to the door switch for this reason (which also meant it wasn't QUITE such a good idea to say rude things about people in there :-)