Until this year we never stayed in our trailer but have a few times already.  I sleep in the bunk and my daughter sleeps on the fold down dinete.  The water pump is below her head and it is loud.  I usually get up early and shower before she is awake but the pump usually wakes her.

Do I have a loud pump or are they all loud?

I found the pump to be loud in my old trailer. I unmounted it, put a piece of foam rubber under it and remounted it. It seems that it was transfering the noise to the cabinet. You may also want to put an insulated style box over it. Their is a product called ductboard that is rigid figerglass insulation that you could build a box out of. I am not sure but don't think overheating would be a big concern.

What you are saying is probably true for my trailer also, it is probably more of a vibration than a noise.  Did the foam rubber make a big difference?