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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  • Tunnah - Thursday, July 11, 2019 - link

    I was on board until the price. I paid £60 for my NH-D14 and expected a price bump considering it's now 8 years old, but nearly double the price is a bit too far. Reply
  • npz - Thursday, July 11, 2019 - link

    EACH fan alone is $30. So $60 out of the $100 of the MSRP accounts just for the fans and they are the best fans on the market. Reply
  • npz - Thursday, July 11, 2019 - link

    It's also more compact than the NH-D14 while having 1 more heatpipe (7 vs 6) Reply
  • sonny73n - Friday, July 12, 2019 - link

    Who gives a damn about 1 more heatpipes. These are buried under a nickel plated plate anyway. Reply
  • tamalero - Friday, July 12, 2019 - link

    It helps transfer heat you clown. Reply
  • SaolDan - Friday, July 12, 2019 - link

    This made me laugh in a crowded plane Reply
  • npz - Thursday, July 11, 2019 - link

    I don't think you'd get anything since the dual plates of the NH-D14/D15 have more surface area but if you're running the fans at high speed, you can replace the front fan with the NF-A12x25 Reply
  • Cellar Door - Thursday, July 11, 2019 - link

    I've been using a NH-D14 with a single fan for 10 years now. NH-A15 for last 5 years - and I have no intention to replace it.

    The upfront cost might seem high but when you realize a cooler like this will last you 10+ years, it is easily justifiable.
    Reply
  • Skeptical123 - Friday, July 12, 2019 - link

    It's a piece of metal... The only real reason a DIY style air cooler "dies" is because mounting hardware/form factor is out of date. The fan is another story but simple getting hit in shipping or ambient dust are big factors and are very replace able. Reply
  • sonny73n - Friday, July 12, 2019 - link

    $30 for a 12mm fan? I can make a fan out of scraps and sell it to you for $3000. Mine will be 100 times better than this Noctua fan, based on price. Reply

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