(This is kind of a duplicate of a subject raised in "General Hardware" but as I am quite interested in the answer, and the General Hardware thread started off being about something else, and the topic is probably better suited to the DIY forum anyway, I thought I'd raise it here too. Mods please delete if this is inappropriate.) One can buy sheets of foam rubber fairly cheaply on the 'Net. For instance, at TW Foam you can buy 2" thick stuff for as little as 84 pence per square foot. I'm sure that this is nowhere near as good as Auralex acoustic foam, but as the cheapest Auralex stuff (at, say Dolphin Music) costs £4.16 per square foot it is substantially cheaper. Has anyone experimented with standard foam rubber to see how effective (or not) it is as an absorber?