Belgian paper recently about the quitest room, an anechoic chamber - I can't even imagine how noise must sound in there. It said the longest anyone has ever been able to remain in it was 45 minutes, a reporter. Because of the sensory deprivation, people start to hallucinate quite fast. The room is used to test the resolve of Astronauts to suppress hallucinations before they are allowed to go into space. It sounds so fascinating, I would love to give it a try, I also would love to find a flotation tank once like John Lilly used.