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 Metro Exodus Enhanced Edition for 30 minutes.
Overall noise output of the ASUS RTX 4080 ROG Strix is very low indeed. The Performance BIOS is already very quiet, with the fans running at 37%, or just 1210rpm. The Quiet mode improves on this further, dropping fan speed to 31%, or 1030rpm. This resulted in a noise level of 32 dBa – the noise floor of my office. In other words, from a distance of 30cm you couldn't hear a difference between the fans spinning or not, it is that quiet!
My sample did exhibit a small amount of coil whine, though nothing major whatsoever and it was barely audible over my chassis fans. This can depend on the specific PSU as well, so that's another thing to bear in mind.