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Before any testing was done with installed systems, each case was tested on its own with fan and power supply. This procedure is to establish a baseline noise level for the system before any other components are added. It tells us how how quiet the stock system can be; adding components can only make it louder, and at best, keep it at the baseline level.
Stock Fan Measurements
The stock fan is a Silverstone 120x25mm model RL4Z S1202512 LIW-3M rated at 0.26A at 12V, with seven "golf ball pock mark" blades. This type of blades was first seen in the Golf fans made by Globe Fan, which is the actual manufacturer. The dimples on the blades are said to reduce noise by 15%. The geometry is OK: The blades' trailing edges are not parallel to the four struts, which suggests that the noise generated will have modest tonal elements.
Sliverstone RL4Z S1202512 LIW-3M fan
The fan was examined and listen to on its own, but measured while mounted normally in the SG05 and SG06, with the cover in place. (This is not a review of the fans, but of the cases.) The case was placed at the edge of a table in the anechoic chamber. Two sets of SPL measurements were performed, one at 1m as usual, and another at 0.6m, at the ISO 7779 (PC noise measurement standard) seated user position.
This is a smooth, fairly quiet low speed fan. One of the two samples had a small degree of chuffing sound, the cause of which was difficult to determine, but it was most afflicted at 12V and the effect became much less audible at lower speeds. 5V is not a usable setting because the fan does not start consistently except at 7V or higher. The usable range is 7~12V (680~1100 rpm) with SPL dropping by 11 dBA between those settings. At 7V, the fan produces roughly half the airflow of the 12V setting, and it is close to inaudible even at 0.6m.
Any noise difference between the two cases falls to the difference between the front bezels. The SG05's more open bezel could be expected to produce lower turbulence noise at higher fan speed while allowing a more direct sound path to the user. The more closed bezel of the SG06 would be expected to block more noise from reaching the user, but perhaps at the expense of higher turbulence noise at higher fan speeds, and possibly reduced airflow due to higher impedance. In other words, on paper, it looks like the contest could be draw.
Empirical measurements and subjective listening contradicted these conjectures, however. The SPL of the SG06 was substantially lower, by 6~8 dBA with the fan at full speed. The noise difference could be easily heard as reduced turbulence noise (whoosh) at all but the lowest speeds. At 12V, very little turbulence noise could be heard from the fan in the SG06; it sounded mostly like a hum. The higher noise in the SG05 is due partly to increased airflow passing against the impedance of the drive cage which blocks much of the top half of the fan. With the much more restricted intake of the SG06, less air seems to be flowing through the case. This could not be measured easily but it could be felt.
The acoustic differences between the two bezels mostly even out when the included power supply is turned on. The FSP300-60GHS
power supply starts with a bit of whoosh from the fan, which then settles down to a very quiet 15 dBA at the 0.6m seated user distance (ISO 7779) . However, this initial quiet is misleading, because the PSU fan speeds up gradually so that by the time it stops increasing in speed (with no load on the PSU) some 10-15 minutes later, the SPL with only the PSU measures 22 [email protected] That is enough to make the SPL difference between the front bezels of the SG05 and SG06 moot when the fan is set to 9V or lower.
The overall quality of the sound from either case is not wonderfully smooth, but nor is it terribly noisy or annoying. It has some tonal elements, mainly from the 80mm fan in the PSU which naturally makes a higher pitched sound than the 120mm front fan and some low level, very high frequency squealing from components inside the PSU, but the overall noise level is still modest enough that it shouldn't be much of a hardship to work next to it for long periods.
With only the front fan going at 9V, the SG06 is very quiet and smooth sounding even at a close 0.6m distance.
Turning on the power supply raises the overall level by 8 dBA @ 0.6m distance. Note the ~1.2 kHz peak caused mostly by the PSU's 80mm fan. The 10 kHz spike is part of the electronic whine from PSU components that may be audible at close proximity by those with good hearing
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