I get the same noise you are talking about when I turn up my 2 gyre 250 wave pumps. Just have to reposition them so the flow isn't hitting the inside box. Another problem I have had in the past is the length of the drain pipe going into the water in the sump. If it is too long it will trap air in the line. My drains are only about 1 1/2 inches under the water level in the sump. As Mixer911 stated, it is scary looking to raise the water level in the rear box but I had to do the same thing, so far so good. Good luck to you and I'm sure you'll get it figured out.