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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  • Drkrieger01 - Friday, July 12, 2019 - link

    While the price for the fan is high, so is its performance. The fans used outperform most 140mm fans, and are very quiet. I'd gladly pay the price for the fan considering they have MTBF's far beyond all the fans you see sold to consumers (typical Noctua MTBF on fans are 150k hours, other brands 30-50k). They are best used on radiators for liquid cooling, or dense-fin tower coolers Reply
  • dqniel - Friday, July 12, 2019 - link

    Nidec fans are still the best for pushing air through dense fins. Reply
  • Showtime - Saturday, July 13, 2019 - link

    I have 140mm Phanteks, and I guarantee these 120mm fans don't keep up with them at the similar decibels. They hold their own against my 140mm Noctua's. Those Phanteks cost me between $10, and $15 each so there are plenty of options if you're willing to research.

    Remember kids, it's not night and day. You're paying double for what usually just a few decibels, or degrees from other good coolers/fans.
  • poohbear - Tuesday, July 16, 2019 - link

    Yes but they last longer, and the quality is topnotch. My uncle always used to say: "I'm a poor man, so i only buy expensive things". Mind you, he lived long before brand name clothes were as ridiculous as they are now. You get what u pay for. Reply
  • tigz1218 - Tuesday, July 16, 2019 - link

    Decibels are a funny thing. Did you know that for about every 10db the perception of loudness doubles? Only a few decibels can make a big difference to what you actually hear. Here is a good article:
  • Death666Angel - Friday, August 2, 2019 - link

    Couple of things on that: The A12-25 is their bread and butter fan that can serve pretty much any purpose inside a case (case fan, heatsink fan, radiator fan). Noctua has cheaper alternatives like the S, F and P series, some of which are available in a redux version with no addons. Normal Noctua fans have screws, anti vibration mounts, a splitter cable, an extension cable and a low noise adapter. I bought two redux NF-P12 1700 PWM fans for 28€ (not on sale). The cheapest option like that from Phanteks would be 30€.
    Another thing: Noctua has a 6 year warranty and if the damages to the item are identified as being genuinely covered under warranty (which unless you bath the fan in liquid is almost always the case) then they rebate the shipping costs. Phanteks website claims 5 year warranty for fans and no rebate for shipping costs.
    And lasty: I have yet to see a Noctua fan die on me. I have most other types of fans die due to some sort of hub or gearing issue (graphics cards, case fans, heatsink fans), even brand names like Silverstone, Noiseblocker, Be Quiet, Asus (which was Delta). So in my experience, depending on the product, the small extra cost upfront is made up with by extra performance, longevity and support. They also once sent me a new mounting kit for the NH-C12P. I probably wouldn't buy the 30€ 120mm fan that is used here, but then I also don't need 2000rpm max and Noctua offers cheaper options on their own.
  • Oliseo - Thursday, August 8, 2019 - link

    Imagine, someone has to take a chance on employing you when you finally leave school.
    It's the people who have to work alongside you I feel pity for due to the stupidity of any manager that does.
  • eddieceidde - Saturday, November 7, 2020 - link

    Doubt Reply
  • mariush - Saturday, July 13, 2019 - link

    A RETAIL fan may be $30 but may cost as little as 5-10$ to make. It's mass produced, already have tooling for it, and so on... Reply
  • Foeketijn - Sunday, July 14, 2019 - link

    In most industries, the BOM is about a tenth of the retail price. So probably even less than that 5 dollars. In case of fans, I can imagine the relative BOM even being less.
    A load of R&D goes into the design of the blade. That's it.
    IKEA can sell you a half decent battery powered screwdriver for less.
    The cost of making it, is not really relevant is it?
    Is it worth the money.
    For me a silent computer is very important. So next time I will use a boxed Ryzen.

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