I get the same on an a6 2018 but mine isn't white noise. Mine is straight up doin blood pressure machine sounds. And then I unlock it and it's like nothing happened. Kinda disturbing - thought it might explode
Okay, wo it's happened again and this time I can say for a fact it was not overheating, the processor should not have been strained it any way, it only had WiFi on, it was not on charge, and it happened at a random moment of the day, and when I hit the power to unlock it, it stopped.
I can tell you now, that it was more than just white noise or some soft background buzzing it sounds like dial up Internet. It's loud and noisy and it freaked me out because i thought it would explode