I've got a Dayton 10" 550CFM axial fan... and the thing is loud.

Not like a helicopter, but it's loud.
I just bought a NuTone 300CFM bathroom exhaust fan... that's more quiet... much more.

You can always build like a "muffler" box, and install your fans in there to keep noise down.
turtle420 Reviewed by turtle420 on . Exhaust fan noise ?? Which are louder the vortex fans or the dayton fans??? comparing same cfm's Rating: 5