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 Fire Strike Ultra stress test for 30 minutes. An idle reading comes after leaving the system on the Windows desktop for 30 minutes.
While the Challenger proved slightly cooler-running than the Sapphire Pulse 5500 XT, it is also slightly noisier. A result of 42dB is still good and this is certainly not a loud card, but it is more audible than the Pulse. Under load, we observed its fans spin up to around 2000rpm, or 52%.