Buzzing noise when USB is connected?
 

I was wondering if anyone else has had this problem, and if they've fixed it. After I plug my phone into the USB port, there's a somewhat-quiet-but-still-audible buzzing that occurs. Even when I lower the volume to 0 it's still audible. Unplug the phone from USB and it stops. I have to turn the volume up a bit before it drowns it out, which isn't a major issue but sometimes I'd like to listen to music a little quieter. 2016 FR-S in case anyone was wondering.

Ground loop. Might try a higher quality cable, but might just be your phone. Older ones can charge 'noisily'