Is it true that we can't tolerate complete silence for long?

I’ve just heard about a room dubbed World’s quietest room room somewhere in the US. Nobody seems to be able to stay in that room for more than 30 minutes. That intrigues me. I know that people usually can’t stand a noisy room, but it is the first time I’ve known that a silent room can be terrifying too. Is it really true that people can’t stand complete silence, or are there factors other than just silence that make that room unbearable?