Fan Noise
In past years, gamers would accept everything for a little more performance. Nowadays, users are more aware of their graphics card's fan noise and power consumption.
In order to properly test how much noise a card's fan emits, we use a Bruel & Kjaer 2236 sound-level meter (~$4,000). It has the measurement range and accuracy we are looking for.
The tested graphics card is installed in a system that does not emit any noise on its own, using a passive PSU, passive CPU cooler, passive cooling on the motherboard, and a solid state drive. Noise results of other cards on this page are measurements of the respective reference design.
This setup allows us to eliminate secondary noise sources and test only the video card. To be more compliant with standards like DIN 45635 (we are not claiming to be fully DIN 45635 certified), the measurement is conducted at a distance of 100 cm and 160 cm off the floor. Ambient background noise inside the room was well below 20 dBA for all measurements. Please note that the dBA scale is not linear but logarithmic. 40 dBA is not twice as loud as 20 dBA since a 6 dBA increase results in double the sound pressure. The human hearing perception is a bit different, and it is generally accepted that a 10 dBA increase doubles the perceived sound level. 3D load noise levels are tested with a stressful game, not with Furmark.
Unfortunately, the Zotac GTX 1080 Mini lacks the idle-fan-off feature that has become standard on most graphics cards today. My guess is that Zotac was very concerned that the card could overheat in a hot, closed case.
Gaming noise levels are very high, too. The card is noisier than both the GTX 1080 and GTX 1080 Ti Founders Edition. Temperatures are extremely low with only 67°C, though, which is probably another safety measure for ITX systems.