Early adopters of the NVIDIA GeForce GTX 1080 Founders Edition were complaining about fan noise issues as the card's fan has a tendency to rev up significantly in RPM, regardless of GPU temperature or load.
NVIDIA looked into the issue and promises to fix it in a soon-to-be-released driver update:
Update 6/1/16 - We are testing a driver fix to address the random spin up/down fan issue.
Update 6/2/16 - Driver fix so far has passed internal testing. Fix will be part of our next driver release.