Sounds very freaky:

They say silence is golden – but there’s a room in the U.S that’s so quiet it becomes unbearable after a short time. The longest that anyone has survived in the ‘anechoic chamber’ at Orfield Laboratories in South Minneapolis is just 45 minutes. It’s 99.99 per cent sound absorbent and holds the Guinness World Record for the world’s quietest place, but stay there too long and you may start hallucinating.

[...]He said: ‘How you orient yourself is through sounds you hear when you walk. In the anechnoic chamber, you don’t have any cues. You take away the perceptual cues that allow you to balance and manoeuvre. If you’re in there for half an hour, you have to be in a chair.’

Freaky!

• More on anechoic chambers.

• The photo up top is from here, and is of an anechoic chamber built by Eckel Industries, the Massachusetts company that built the world record vault for Orfield.