[Q] High-pitched whining noise while plugged into charger
I have a rooted stock 4.4.2 Nexus 7, and I'm encountering a really weird problem where there's a persistent high-pitched whining noise that seems to come out of the speakers whenever it's plugged into a wall charger. I tried the stock charger + cable that came with my device as well as 2 other third-party chargers all with the same results. Meanwhile, charging it via USB connected to my computer doesn't produce that sound at all.
Does anyone know if there are any tweaks or settings that could be causing this? I looked in the FAQ, and I only see a giant thread about static while at low volumes, but this looks to be a completely separate problem since it's unrelated to volume settings & it happens when I have no sound playing at all. Googling this returns a bunch of results with people's chargers making noises, but not the Nexus 7 itself.
If anyone else has had this problem and can offer any insight, that'd be appreciated. It's not the biggest deal in the world, since I just have to make sure I'm not in the same room when it's charging so I don't get annoyed, but if I can fix it, that'd be great.