I have a SRO XP1000 sss and I can't hear a thing unless I get my ear right up next to the air intake. A friend of mine has a Vertex Alpha and it is literally dead silent. I couldn't even hear a hiss from the air intake.
I have a bubble magus nac 3.5 and its great but for your tank Vertex omega 150 this is the skimmer I will purchase soon its build quality, function and looks make every other skimmer in the price range seem pathetic