According to its label mine's the original 1995 rubber feet mounted Shurflo in a dinette underseat locker and apart from a gentle whirring when it's in use it's as good as silent. Mind you, the 1995 internal furnishings and units are of pretty solid wood, unlike today's eggshell thin shiny plastic mouldings.
If the motorhome manufacturers adhered to the Pump manufacturers fitting instructions there would not be a problem. They incorrectly fit angle bends close to the pump, they mount them on thin panels which act like a drum and magnify the noise and they do not fit a length of flexible pipe to and from the pump.
Look at your pump manufacturers guidance on installation and follow that guidance, you will end up an acceptably quiet pump.
Ours (2021 Burstner ) is pretty quiet. Have been known to leave it running (tap slightly open) and not notice. It is mounted inside the water tank - I guess that makes it quiter than external mounted pumps?
However, I was parked next to an older van (also Burstner) recently and I could hear when they had a shower and went to the toilet. It made a right racket!
The pump in our Hymer is a submersible one and it is very quiet. Much better than the Sureflow pump in our previous Adria. When one of us uses the toilet in the night the other is no longer woken up with the flush.
I fitted a Shurflo pump and a Fiamma damper using flexible pipe work, the pump sits on a thin plywood and foam base resulting in a very quiet pump. The original Whale submersible pump was a lot noisier.
Ours is noisy. It is quite powerful for a van (Shurflo 40psi), but also mounted on dampening material, on flexi connecters and boxed. Still noisy.
A couple of years ago I built a few vans for a friend. He had bought Fiamma 20psi pumps. When we tested the system in the first van, it was almost silent. We were both a bit bothered by this (pumps are usually a bit audible) so quickly ripped the covers off to see what was wrong. Nothing, it was just quiet. We put it down to luck, but after fitting out another 3 of his vans with the same pumps, they were all quiet.
So, I thought I'd try a Fiamma in our van. 20psi wouldn't cut it (instant hot water system) so I ordered the 30psi model. Noisier than the Shurflo. Sent it back.
In the Vario, I'm going to fit separate pumps on the hot and cold (hoping this solves an issue with instant hot water boilers). Very tempted to try the Fiamma's again, but this time 2x 20psi.
Our Sureflow pump is great! eh? what did you say? Oh!..... half past Three!
We nickname ours Woody, as in woody woodpecker Pressure is good, plus we don't have those silly taps with microswitches needed with submersibles so we are happy with "Woody" = pressurised systems less to go wrong, better shower pressure IMHO.
My advice would be check out your Sureflow pump installation & its mountings, if additional sound insulation is needed via rubber matt or similar, then check out what's available on Google, loads of double sided isolation double sided sticky base plate options available. LES
Our Autotrail has a shureflo pump and its very noisy. Has been from the day we bought. Thought it was normal! Other half complains every time its used. Hadnt thought about refitting it on dampers. Thx for the advice.