If it directly mounted to something? Like into your wall, etc.
What makes the noise is all the material around vibrating. (In my experience.) I do not have experience with tents so I'm not sure if it's possible, but, my first cabinet had the rigid metal piece of the inline resting right on the wood. That sounded like crap. Now I have everything hanging from the ceiling and the pipe basically floats through the hole and the gap is sealed with foil tape. Now the only thing you hear is my box fan vibrating on the wood floor... that's next to go.
If you don't get what I mean, run the fan in your hand. If it sounds less noisy then when it's mounted - vibrations are your issue. If the noise is the same, then maybe look into dynamat or just sound proofing your ceiling so you don't hear it from upstairs. Friends I know did that.
Bud D