I have wet/dry sump on my 72G w/ overflow and it isn't that noisy at all. The water lvl in my sump is equal to the height of the bioballs. IMO
the noise seems to come from the water falling into the sump when trickling through the bioballs. My aquarium is in my main television viewing room and my wife is very picky when it comes to noise and asthetics (haha, whose isn't) and she doesnt have a problem. Hope that helps!