Changes to How We Benchmark Noise
Typically, we use a regularly-calibrated Voltcraft SL-400 sound level meter with data logging for noise benchmarks run in our German test lab. The SL-400 doesn’t really go beyond 10 kHz, though, and is useless for picking up coil squealing.
PowerColor's Devil13 HD7990 drove us nuts with its high-pitched whine, though, so we had to make a change to our testing methodology in order to reflect this. Now we're using a calibrated and vibration-free suspended studio microphone.
PowerColor's Devil13 HD7990 would have done well were it not for the high-pitched coil squealing beyond the capacity of most sound meters. As a result of this whine, however, it finishes in last place.
We had two of these cards at our disposal: one in Germany and one in the U.S. Both exhibited the exact same behavior to different degrees. The severity of the squeal varies depending on resolution and load, but it's definitely an irreconcilable issue that we wouldn't be able to overcome on a $1000 graphics card.
EVGA's GeForce GTX 690 is the quietest card when it comes to gaming. This shouldn't come as a surprise because it dissipates the least amount of heat.
All three boards fare well enough, though. PowerColor's Devil13 HD7990 is the loudest, but it still makes less noise than AMD's reference Radeon HD 7970. That's a testament to the effort all three vendors put into prioritizing acoustics, and we can only hope that AMD's own engineers are paying attention.
Under full load, HIS' 7970 X2 simply cannot keep up, losing to EVGA's GeForce GTX 690 and PowerColor's Devil13 HD7990. In fact, it even falls behind the reference Radeon HD 7970 that bothered us so much when we first reviewed it. None of the AMD cards can claim a victory, though. They all generate in excess of 50 dB(A), which is just too loud. Only EVGA's solution stays under that threshold.
Fortunately, most folks won't be pushing their cards this hard for any extended period of time, making the two other usage scenarios (idle and gaming) more important to heed.