Next up, we took our new test bed and re-worked our sound tests a little to better categorize both the levels and characteristics of the noise produced by each case with the accompanying test hardware installed and operational. No case won or lost overall by a clear margin, but there were still distinct victories in smaller areas.
(Sound tests conducted in an ~18dB ambient level environment)
First, for a better frame of reference, we assembled our test bed on the open work bench with our Zalman power supply far enough away that its main fan didn't even turn on. Both of the Zalman coolers - the CNPS-7000 Cu on the CPU and the VF-700 Cu on the GPU - were given 5 volts instead of 12 to keep their levels acceptable for desktop use in a near-silent environment. This open air test bed proved to be nearly silent, registering a record low from the CPU side of the computer of 23 decibels.
An open air computer is hardly practical though, and a good case should actually be able to help bring already quiet levels like these down further with just the right amount of well-designed sound insulation, and much to our surprise, the inexpensive MicroFly did the best job of this! Until we did our loading test, the Ultra case had by far the best characteristics of its sound. Subjectively, it was no different than the open air setup, a very prestigious claim to say the least. When kicked into high-gear unfortunately, the case began to sing a new tune as the included power supply's fan went into its other speed zone, creating a noticeable motor bearing noise along with the whooshing sound of moving air. 3.5 is still a good rating for any desktop PC case (remember that these are 1-10 ratings), but if the environment was quiet enough, a highly-stressed MicroFly might be annoying enough for some people to regret not getting a quieter solution. We did try putting both system fans on 12 volts to see if the power supply would stop going into high-gear, but it still did and then the case was even louder at idle.
The Aria also did a great job of staying nearly as quiet as the open setup, but its power supply fan had just a hint of bearing noise that, thankfully, blended with the air sound from the blower on 5V to get mostly lost in the overall sound signature. For a case as warm as the Aria, it might have helped a lot to allow for a few more active cooling elements, or at least include a power supply that can increase the fan RPMs at the higher temperatures we measured.
PC Design Lab's Qmicra performed admirably with the Zalman supply and single Tri-Cool fan, but when all four fans were installed (and even only running on five volts each) the sound of moving air was certainly noticeable, both to our ears and the dB meter. Strangely enough, the sound-dampening material obviously worked for the dB meter, as the install with the CNPS 7000 cooler registered lower levels than the open-air bench both from in front and the top, but we still noticed the slight hint of extra moving air and motor noise from the single Antec Tri-Cool 80mm fan. We actually speculated that this might be because the good performance of the sound insulation material would make the Tri-Cool (the only active fan immediately next to an open grill) more noticeable without the other fans being heard, and this theory would also explain the almost identical measured levels.
Before wrapping up, it should be reinforced that all of these setups were comfortably quiet - perfectly suitable for use in 90% of computing situations, and a couple even capable of handling the tricky task of working in an audio-sensitive environment, particularly if a high-powered portable machine is desired. Compared to smaller cases we've looked at before and a few famously noisy Shuttle computers, this is a welcome change for the SFF industry.
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