Here's a video response^ by a guy who wanted to test this assertion. He spent about an hour in one at BYU, and seemed comfortable enough throughout. Interesting points: at around the 16 minute mark, he verbally estimates his time at 8 minutes; after the 45 min is up he asks for the lights to be turned on, and gets no response from the people outside the chamber. He calmly finds the door by using his cell phone as a light.
I am glad you sent me this video, but again the important part is that the test conditions are not the same as the original article. As much is mentioned in the video notes and comments... I do agree though that my source article is not exactly scientific, and it may be some kind of bias being introduced by the test participants.
that article is wrong wrong wrong. I hate that article. I've seen it many times, it just sounds like some dumb reporter got into an anechoic chamber and thought it was crazy so he says you will start hallucinating and nobody can stand it for more than 45 minutes. that is plain wrong. I've been in an anechoic chamber to setup equipment to be sound tested, it's a very weird sensation to have the pressure of sound lifted off of you, and to hear your insides working, but everything about that article I loathe.
edit: oh what the hell, I never saw the certificate picture of the world record before, and that chamber is only -9.4dBA when there are plenty now past -12dBA (though I don't know the rating of the chamber I was in)
^ https://www.youtube.com/watch?v=mXVGIb3bzHI