Hello everyone!
I have this problem with my VW Passat B8.
Whenever I enter the car I hear this static sound from the speakers provided that the monitor is turned on.

It's very similar to the sound you hear when you're searching for stations on the radio, and it increases or decreases with volume.
Sometimes it disappears and appears again (or it might be that I get used to it and forget about it, not sure).
There's a Helix subwoofer in the trunk instead of the spare wheel. I wonder if this accessory is programmed incorrectly?
Does anyone have any idea what the cause could be?
Thanks in advance.