I personally questioned if sound, or, really, the absense of it could have THAT dramatic of an effect (especially in the short amount of time), especially when me, personally, try to go out of my way to find as quiet of an environment as I can (save for my computer, she's a little rackety)
This video someone decided to put that myth to a test and wound up staying in the chamber for an hour just fine.
I can't help but sit here and wonder what it would be like to set up shop inside that chamber and actually do some mixing...how might the final result sound?