Bro I recently had this same issue and tried everything to fix it. I tried padding the pvc, limiting the flow by valve, bracketing the pump, moving it in several different positions and everything. It was so loud I could hear it upstairs, after doing all that I come home and its whisper quite. My brother was maintaining the tank and added more water to the sump and moved a sponge blocking the return. Now the pump is whisper quite. I have a aqua euro an off brand name I can barely hear it now. You have a more well known brand pump this should not be happening. My pump is the highest rated available and its quite. I was about a day away from purchasing another pump and went to 2 stores to actually check them out. Turns out all the vibration and noise had something to do with restrictive flow and not enough water in the sump. Try removing all of the sponges and removing anything that can be restricting flow. If flow is being restricted the pump will become louder. I think this is your problem. I swear I tried everything in the book and my stupid brother fixed it by accident and saved me dropping another couple hundred bucks. Like I said my pump is some off brand and its no longer loud. It must have something to do with this...