My pump is mounted on a shelf that was held down by two screws. One came loose, so the shelf rattled, amplifying the noise the pump makes. Adding a few screws to the shelf helped a lot.
The noise is vibration reverberating through the trailer. Best way to lessen the noise is to isolate the pump so it can shake but not transfer the vibrations. Soft Rubber blocks could be used under the pump and mounted so the hardware does not go from the floor to the pump. Think of a motor mount and how it isolates vibration. I am sure there is something out in cyberspace that could help.
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