Hazmat I got a vortex fan made in canada. It's about 49db's. I build a box and installed it inside with rock wool sound insulation.I put it up in the attic and I dont here it at all.The one I have is a 6" 449cfm's 49db's it exchanges the air in the room around every 25 mins. .My room is 2'x8'x8' width times length times height will give you the cube feet of the room.you can go from there to see how big of a fan you need.