Ours was sometimes louder than others, one of the complaints I have heard about the 12V is the compressor noise. The propane makes no noise but I've found that they don't work as well in heat or while traveling, I'll take the noise.
Hi folks, without additional details it is difficult to comment with any certainty.
Could it be compressor noise? Could it be the ice maker solenoid valve trying to fill the ice maker(if you have one).
If you have a ice maker, try raising the bar to the off position to see if your concern stops.