In another thread, the point was made that the fans mounted on the main case panels -- back, front, sides, top -- are often the primary determinants of noise. This is an issue I refer to in the Case Basics article --neologan wrote:I grabbed an R3 several days ago. I'm very happy with the build quality and performance.
Excellent case, though. I've got to say, however, that it hasn't really made a big dent in noise levels.
"Good acoustic damping can reduce the noise by several decibels, and more at higher frequencies. But the need for airflow leaves at least a couple of open fan holes through which fan and HDD noise always come through. The best approach is to get the noise of those components to a minimum first, and then consider whether acoustic damping might help further."
Thicker, sturdier, better damped case panels can help lower the noise of components inside the the case, but the front or back panel fans are practically out of the case anyway, so the direct airborne noise from them cannot be reduced by a better case. If a case provides 10 dB reduction through its panels, then the CPU heatsink fan in its center will benefit... but the open back panel vents lets the sound out directly, so the overall sound you hear from that fan is not -10 dB, it will depend a lot on what direction you measure from. Perhaps from the front, with a closed door on the case, the fan noise will be close to -10 dB. But definitely not from the back.
If you measure the noise of cases from 1m directly behind them and mount the same CPU HS fan in all of them, I doubt we'd see more than a 1 dB difference in SPL among cases, maybe another dB lower for the ones with are heavily damped with sound absorbent materials. Mount that same fan on the back panel, and there'd be no variation in the SPL at all. That's assuming panel vibration is tightly controlled -- for example, if the fan is soft-rubber grommet mounted. (You might then ask, would a long well-damped tunnel though which the fan blows air out help reduce the noise? The answer is no, that tunnel would introduce its own air resonances, which would actually accentuate and amplifiy certain aspects of the fan noise.)
So going back to your LianLi vs Fractal noise perception, it's not a surprise. If noise from vibration in the LianLi was well controlled, and the quality of the fans in the panels of the 2 cases are similar, there's not much reason for any difference. I'd be surprised if there wasn't at least a subtle qualitative improvement -- thin aluminum panel easily pick up vibration from HDDs & fans, and lend a certain level of haze in mid and higher frequencies from overtones.