For what it's worth, my experience with installing a fuel pump is
here. I suspect that the Facet fuel pumps (and, of course, identical ones that are branded differently) get noisy when there is a fuel bubble in them. Probably pretty easy for that to happen, if you install it as the instructions specify--you have a big loop of fuel line to get over the rear axle, then to the bottom of the pump, and finally another loop from the top of the pump to the rest of the fuel line. This creates plenty of opportunity for bubbles to lodge in the loops, and, if they get large enough, to reach the pump. I've only noticed mine get loud once or twice, and I suspect this was the reason.
As you can see from the pictures, I mounted mine on a couple layers of bicycle inner tube. I don't know how much good that does, for minimizing noise, but I suppose it can't hurt. Finally, I think I might have mounted it a little too high; ideally, you want to keep it low enough so it is always below the fuel level in the tank. This, plus a reasonably large loop at the outlet side, will tend to minimize bubbles in the pump.