I can't hear just one of them running when inside the sealed up cab, the 2nd fan has not kicked on yet because of the cool weather. I am pretty much deaf in one ear so that may factor in so thats why I hooked up 2 lights inside the cab so I could tell when they were kicking on.

 

When I first saw that pic, they reminded me of the industrial fans you see attached to a walk-in freezer that can move ridiculous amounts of air. At least the cages looked like them anyway.