FLStudio ASIO driver. This seems to have happened after I installed FLStudio 20, all though I used it when recording a video about the FL20 beta, which worked fine. I did a search and found a similar post ...
FLStudio ASIO / Primary Sound Driver
0:16 - 0:22 - Kontakt Audio
I can hear this noise from my headphones as well so it seems to be routed to my PC output. When playing a bass note using my interface ...