The reason I believe it is quiet is mostly because of this box build.
http://www.overgrow.com/edge/showthr...5?pagenumber=1

That person did so much work to make that box super stealthy and I don't think she/he would have spent all that time making it look like a simple desk if the exhaust was making enough noise you'd think a hurricane was comming (especially for 24/7 running). I really want to go with one of those fans simply because of space. I will not have enough room to fit in an 18" fan plus the cardboard box crap (lol) and the control/motor sections of that fan. Thanks for any info.