You'll have to raise your emergency drain, and make the water level in your outside box higher than the top opening of the nut connecting the two. This'll make it dead silent. I battled with this as well, and ended up pulling the tubing that comes with it for the emergency drain and replacing it with a piece of red PVC tubing that was slightly longer. I'll try to snap some pictures when I get home from work this afternoon. Basically whats happening is the water level in the outside box will match the inside box, and the water level is to low so the water has to fall more. If you raise the water level it doesn't have as long to travel and therefore isn't as loud.