I have 4 of them. My first is extremely quiet, one is normal (as loud as an ac110) and the other two are a bit louder, but not as loud as some filters I have had. I still like them those, especially for their biowheels, plus they come with a spray bar (great idea) and a grey container thing that I put biomax in, but that is just my setup.
All in all, my favorite HOB filter. Switched from owning 5 ACs, smallest being AC70.