Buzz from fridge even when switched off?

[Hotel California]

When my 2012 Cali is on hookup is it normal that i notice a buzzing sound coming from the fridge when the fridge is turned OFF ....!? Cali sitting in garage and fridge not worked for days.
When not on hookup , NO buzz ...
Need to check it with engine running but was not gonne start up specially for that , check it out this weekend
Cali was on hookup in my garage for topping up the batteries and when sitting in the back i noticed it....
The lid of the fridge was open and you can hear a light buzz comming out ...normal ?

 

[calikev]

It is more likely to be your battery charger buzzing

 

[WelshGas]

Is it actually the fridge or the battery charger unit situated below the fridge resonating?

 

[Hotel California]

Battery charger makes sense, just was finding it strange i heard a sound even nothing was switched on , when on hookup on site theres usually always something running but now it was all swithed off,the lid of the fridge was opened to ventilate and to mee it seemed to come from inside the fridge....no there was not a bee in it :lol:
Try so stick my head in cabinet under cooker and look thru the round opening to check where it actualy is coming from