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 the 3DMark Time Spy stress test for 30 minutes.
Noise levels are actually unchanged compared to the RTX 3080 Eagle OC. Where that card runs its fans at 1680rpm, the RTX 3090 Eagle OC does increase this slightly – but only to 1760rpm, and that wasn't enough for our sound meter to register increased noise levels. It's not a silent graphics card, but you'd still be hard pressed to hear it over your case fans, so I don't think this is any cause for concern.