Exploring Pump Noise
Let’s go back in time a few days to right before the Radeon R9 Fury X’s launch. Our German team (the guys measuring thermals, power and acoustics) were only able to test the new card for a few hours due to a scarcity of press samples. But this short time period was enough to give us an earache. Our colleagues reported the same problems, which confirmed the existence of a whistling noise. In addition, there was some kind of buzz. The latter is a low-frequency, oscillating grinding noise. These noises combined to form annoying acoustic fireworks.
Since we weren’t the only ones who contacted AMD about this, all reviewers received a preemptive email that was supposed to calm and reassure people:
Very small batch?! We wanted to know just how small this batch really was, and got our hands on our own retail sample from Newegg, just as a customer would. Our model was made by XFX, and we'll say more about it in a small footnote at the end.
Apart from the Cooler Master label being somewhat off-center, our press sample and the retail board, along with their pumps, are identical. By now, there’s talk on some forums about other labels and even engraved Cooler Master logos, but we haven’t seen a card like that in the lab yet.
The retail card’s noise profile is different from that of the press sample in the sense that the XFX card doesn’t just have a whistling noise, but also a lower saw-like noise. Really, it sounds like a buzz saw with an oscillating out-of-balance blade. It even includes the saw’s motor noise. The graphics card’s obviously not as loud, but the acoustic profile is quite similar. Consequently, we’ve labeled this noise “buzz.”
We tried to trace the origin of the sound with a special microphone designed to measure structure-borne noise. This led us to where the small heat pipes are connected above the voltage converters. Even though these are designed poorly from a flow perspective (sharp bends, unnecessary decreases in diameter, possibly a rough inner surface), they were neutral as far as the noise was concerned.
This means that micro-bubbles aren’t the culprit. This conclusion is confirmed by the fact that decreasing the pump’s voltage to slow it down halves the whistle's frequency, but doesn’t make it any less loud. All that remains as a possible source is the pump itself.
