I just registered to share the below as it fixed an issue which caused me lots of frustration.
I experienced a rattling, loud fan noise with a brand new EVGA GTX 1070. The fans only spin on start up or when under load / temperature. So the sound was not constant. But during games and benchmarks it was very loud. The local dealer exchange program (Australia) is quite cumbersome and time consuming so I was not that happy that I have to exchange the card. (this card is 650 A$ here)
I noticed a small brown cable under one of the fans. On the outside of the fan blades on the edge of the case. Most likely for power supply to the fans?!
When rotating, the fans hit this cable and caused the noise.
I was able to push the cable down / outside so that the fan does not hit the cable anymore. Used a small screwdriver (while the card was uninstalled ofc).
This should not have made it through quality control. Cant imagine that something like this happens in transit in a perfectly new, packed sealed box.
Hope this helps.
Thanks.