What I found when I went down to the pond to open the box and inspect the pump is that it has a vibration going that worked it over and up against the edge of the box which was causing a lot of the noise. I don't know what the vibration is about but I hadn't opened the wooden container box for the past few months at least. I moved it back to the center and away from the sides and couldn't see it visibly moving but I am sure there will be creep happening again with the vibration. Now it is back to just a humming noise but one I can hear from 30 yards away on a still evening/morning that wasn't that distinct before. The boils in the pond don't seem to be troubled and appear to be getting good air flow. I am relieved to say the least knowing that the awful part of the sound was actually the rattling with the box. I will disconnect it this weekend and bring it up to the house to open up and see if there is anything visible to me that may be causing the vibration.