Hi, Laurence!
There will be no noise when on electric. When turned to gas, you may hear it ignite...or not, depending on how good your fridge cabinet is insulated from noise. If there is no beeping or flashing lights, you are good to go!
Then all you have to do is wait. And trust me, 2 hours is NOT long enough! Lol! They do tend to cool a bit faster on gas but no big. Turn it all the way up, put a thermometer in the fridge and freeze and give it a good eight hours or so, that is what I do. If it doesn't cool in that time then you can worry!
Good luck!