We take our noise measurements with the sound meter positioned 1 foot from the graphics card. I measured the noise floor to be 32 dBA, thus anything above this level can be attributed to the graphics cards. The power supply is passive for the entire power output range we tested all graphics cards in, while all CPU and system fans were disabled. A reading under load comes from running A Plague Tale: Requiem for 30 minutes.
The B580 is able to maintain such low temperatures while also running the fans very slowly. In my testing, they only ramped to about 1370rpm during our thirty minute stress test, resulting in a noise reading of 33dba. It's not silent, but it's very, very quiet.