Testing Methodology

Although the testing of a cooler appears to be a simple task, that could not be much further from the truth. Proper thermal testing cannot be performed with a cooler mounted on a single chip, for multiple reasons. Some of these reasons include the instability of the thermal load and the inability to fully control and or monitor it, as well as the inaccuracy of the chip-integrated sensors. It is also impossible to compare results taken on different chips, let alone entirely different systems, which is a great problem when testing computer coolers, as the hardware changes every several months. Finally, testing a cooler on a typical system prevents the tester from assessing the most vital characteristic of a cooler, its absolute thermal resistance.

The absolute thermal resistance defines the absolute performance of a heatsink by indicating the temperature rise per unit of power, in our case in degrees Celsius per Watt (°C/W). In layman's terms, if the thermal resistance of a heatsink is known, the user can assess the highest possible temperature rise of a chip over ambient by simply multiplying the maximum thermal design power (TDP) rating of the chip with it. Extracting the absolute thermal resistance of a cooler however is no simple task, as the load has to be perfectly even, steady and variable, as the thermal resistance also varies depending on the magnitude of the thermal load. Therefore, even if it would be possible to assess the thermal resistance of a cooler while it is mounted on a working chip, it would not suffice, as a large change of the thermal load can yield much different results.

Appropriate thermal testing requires the creation of a proper testing station and the use of laboratory-grade equipment. Therefore, we created a thermal testing platform with a fully controllable thermal energy source that may be used to test any kind of cooler, regardless of its design and or compatibility. The thermal cartridge inside the core of our testing station can have its power adjusted between 60 W and 340 W, in 2 W increments (and it never throttles). Furthermore, monitoring and logging of the testing process via software minimizes the possibility of human errors during testing. A multifunction data acquisition module (DAQ) is responsible for the automatic or the manual control of the testing equipment, the acquisition of the ambient and the in-core temperatures via PT100 sensors, the logging of the test results and the mathematical extraction of performance figures.

Finally, as noise measurements are a bit tricky, their measurement is being performed only manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being acquired via a laser tachometer. The fans (and pumps, when applicable) are being powered via an adjustable, fanless desktop DC power supply and noise measurements are being taken 1 meter away from the cooler, in a straight line ahead from its fan engine. At this point we should also note that the Decibel scale is logarithmic, which means that roughly every 3 dB(A) the sound pressure doubles. Therefore, the difference of sound pressure between 30 dB(A) and 60 dB(A) is not "twice as much" but nearly a thousand times greater. The table below should help you cross-reference our test results with real-life situations.

The noise floor of our recording equipment is 30.2-30.4 dB(A), which represents a medium-sized room without any active noise sources. All of our acoustic testing takes place during night hours, minimizing the possibility of external disruptions.

<35dB(A) Virtually inaudible
35-38dB(A) Very quiet (whisper-slight humming)
38-40dB(A) Quiet (relatively comfortable - humming)
40-44dB(A) Normal (humming noise, above comfortable for a large % of users)
44-47dB(A)* Loud* (strong aerodynamic noise)
47-50dB(A) Very loud (strong whining noise)
50-54dB(A) Extremely loud (painfully distracting for the vast majority of users)
>54dB(A) Intolerable for home/office use, special applications only.

*noise levels above this are not suggested for daily use

The Noctua NH-U12A CPU Cooler Testing Results, Maximum Fan Speed (12 Volts)
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  • eastcoast_pete - Thursday, July 11, 2019 - link

    For question 1. "It refers to the 212 cooler, the Noctua is obviously already shown. Reply
  • Mil0 - Friday, July 12, 2019 - link

    I second the suggestion for comparing it to the wraith (spire), esp with Ryzen's PBO. Reply
  • npz - Thursday, July 11, 2019 - link

    One thing I would like to see is in addition to standard dB sound loudness, is frequency spectrum. Two fans of the same dB can sound vastly different depending on the frequencies with some fans being intolerably annoying despite not being loud. Reply
  • Ryan Smith - Thursday, July 11, 2019 - link

    Note that this is already taken into account to a large degree with A-weighting, which we use. It doesn't necessary capture "annoying", but it accounts for how loud certain frequencies are perceived. Reply
  • npz - Thursday, July 11, 2019 - link

    Thanks for the info. Saw the db(A) so I see the confirmation. But A weighting emphasizes upper midrange and really de-emphasizes the lower freqs while just cutting off higher frequencies... I found sometimes some fans have a vibration that can be detected with lower freqs. And sometimes those vibrations / hums transmit through the heatsink into the case and cause weird resonances. At higher speeds I find some fans have a frequency component that permeates through most modern cases (clear sides/glass sides with gaps) Reply
  • Death666Angel - Friday, July 12, 2019 - link

    At that point you aren't testing the fan anymore, you are testing the whole system. So unless someone has 100% the same components and tightens the screws exactly the same etc. it is a useless test unfortunately. Reply
  • Edkiefer - Thursday, July 11, 2019 - link

    I always liked the NH-U14S there going for low 60$ (about same as NH-U12S). You do need a case to support the height. Reply
  • LoneWolf15 - Thursday, July 11, 2019 - link

    I'd absolutely love to find out how the newest Noctuas (UH12A, NH-U14S NH-D15, NH-D15S) compare to the older NH-D14, NU-U12S, and the Thermalright TRUE 120.

    The results on Noctua's new gear is amazing, but I contacted Thermalright to ask about heat dissipation for my TRUE Black 120 from 2008, and found it's rated for a stunning 240 watts. I have two Noctua Redux 120mm 1300rpm fans on it and it's keeping a Core i9-9900K (running all eight cores at max turbo 4.8GHz at 100% usage in Folding@Home) stable , a bit over 80C at 160+ watts load under constant use. An eleven year old (admittedly heavy nickel-plate copper with six heat pipes) cooler. I'm still impressed.

    I'd love to know how far we've really come since the D14 and TRUE120 just to see if there's a significant difference.
    Reply
  • npz - Thursday, July 11, 2019 - link

    I have the Noctua Redux P12s and the NF-A12x25 used here. I find the NF-A12x25 much quieter at 1300 rpms with about the same airflow. If you're satisfied with that level of noise then you can run NF-A12x25 at 1600 rpms or maybe even 2000 rpms for better performance. Reply
  • Oliseo - Friday, July 12, 2019 - link

    I run a Corsair 115i Platinum (280mm) AIO on my i9 9900k, running at 5Ghz all cores with no AVX offset. (Uncore at 4.8)

    It never goes above 72 degrees, when running 100% rendering 3D models. (Where AVX is used heavily).

    I do have the Noctua NH-D15 on my sons i7 9700k, but it's simply not as good as my AOI.
    Reply

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