Noisy refrigerator

We’ve just taken delivery of a new Fairford camper van and are on our first trip away. The refrigerator runs on all electric, it isn’t designed to work on gas. It is a Dometic.
From time to time it makes a lot of noise compared with our old van which we had for seven years and the fridge in that was completely silent in operation at all times. 
Reading the instructions I think I’m hearing the compressor running to bring the fridge back down to temperature. I’ve set it to a  ‘silent’ operation (limited to eight hours the instruction book says) but it still comes on after a short while even on that setting. If it comes on during the night like it is now then I shall have to switch it off.
Does any other owner have this issue? Second, am I doing anything wrong?
Any wisdom you can offer would be much appreciated before we go back to the dealer.

Absorption fridges as previously fitted are silent, compressor fridges do make some noise I believe, I've never used one.

My DC only compressor fridge is inaudible inside the van and only just audible through the external vent. Even then all I'm hearing is the fan over the heat exchanger.

I have known instances where the compressor or related pipework has been rattling against something.

I also have one of these dometic compressor fridges and you soon get used to it and won't even notice the compressor running

Mick, you are not doing anything wrong.  I have the same fridge as you, and in the past 9 months we have travelled nearly 11,000 miles across Europe from Italy to Norway.  

The fridge does make more noise inside the van than an absorption fridge, and I have to confess that for the first month I longed for the old absorption fridge we had in the previous van.

However, you quickly get used to it (and I am a light sleeper).  It is (IMHO) a much more effective fridge than an absorption, slightly bigger because it doesn't have the absorbtion mechanics behind, and keeps good temperatures (we measure constantly with internal bluetooth probes).

I would not however, keep it on silent, because it is not at its most effective.  We have found that position 3 on the dial is best, and it stays there all the time, day and night.  

It cuts in and out, blows cooler air into the van, but I don't notice it now.  There is no point in going back to the dealer, as the fridge (from your description) is working as it should.  Give it time.

I've got a similar fridge in the Celex and, as Big g and Rocky have said, you just get used to it. You should find that you brain just filters the noise out.

However... two related factors: As The Bargee says, if there is something behind the fridge that the compressor is touching, it can really amplify the sound. And if it has a fan, you may be able to make it a bit quieter by fitting a slightly bigger fan - I did that on my Waeco (now Dometic) and it did make a difference. The fans are generally the same type as fitted to computer cases, so they are not expensive.

Thank you for the replies, every one interesting. 
I took it back to the dealer today and I’m glad I did. I was told that the compressor assembly at the rear of the fridge had become detached and was knocking against two pipes. All was put back together properly whilst we waited and the unit is now running very quietly. 
Yes, there is a little noise which we’ve never had from any fridge in nearly forty years of caravanning but it is now as such a low level as to be acceptable.
The dealer also sorted some catches which were not closing properly, eased the sliding toilet compartment sliding door and adjusted the water tap under one of the seats that regulates the flow of water to the sink.
The internal light on the fridge also doesn’t work and it will be recalled when the replacement part is received. You can no longer just replace the bulb, it needs a complete unit including all the display and buttons! Progress, eh? 
We are now happy customers.

That sounds like a good dealership, nice to hear .