I mentioned this in class on Wednesday. They like to challenge people to sit in this chamber in the dark and a lot of people start to hallucinate after a while.
http://www.dailymail.co.uk/sciencetech/article-2124581/The-worlds-quietest-place-chamber-Orfield-Laboratories.html

They do a nice job of explaining things in this video.
https://www.youtube.com/watch?v=i_Rl98sqz6o&feature=youtu.be&t=2m45s