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 manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being recorded 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

Introduction & the Cooler Testing Results
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  • meacupla - Monday, August 14, 2023 - link

    Nidec and Sanyo make good motors and bearings, but their fan design isn't as well refined as Noctua's.
    Delta only sparks images of server rack fans that push a lot of air, but are super loud, and can't be quieted down, because they use a really loud double ball bearing for longevity.
  • Silma - Monday, August 14, 2023 - link

    I've been a fan of Arctic coolers ever since my first purchase there, an Arctic Freezer 33.
  • Leeea - Wednesday, August 16, 2023 - link

    I would disagree.

    For a person willing to do their research I feel there are better options available that yield better results per dollar in every metric.

    The problem is, to much research needs to be done, and buying noctua is the safe easy choice.

    as a result, I own a lot of noctua fans. :(. Trying to get away from them now that manufacturing has moved out of Taiwan into China. (look it up on the internet)
  • meacupla - Tuesday, August 8, 2023 - link

    I hope you guys get a Deepcool Assassin IV and Noctua's LCP 140mm fan to test out
  • PeachNCream - Thursday, August 10, 2023 - link

    It's hard to take any product seriously that has the word ass in the name twice. Double the butt cheeks, double the cooling is probably the implication, but the "in" part...hmmmm....
  • mode_13h - Monday, August 14, 2023 - link

    I think that probably says more about you than the product. I've never seen the word assassin like you suggest.
  • PeachNCream - Tuesday, August 22, 2023 - link

    I'm not surprised you haven't heard that particular pun. Over the years you've demonstrated a dour life disposition.
  • Sivar - Tuesday, August 8, 2023 - link

    Noctua NH-D15: The only PC product released in 2014 that still leads the pack in 2023.
  • meacupla - Tuesday, August 8, 2023 - link

    Arguably, in the 120mm tower category, nothing has surpassed the Ultra 120 Extreme when paired with a noctua A12-25 sterrox
  • mode_13h - Tuesday, August 8, 2023 - link

    It amazes me that none of these coolers with "direct-touch" heatpipes can approach the D15's performance. That just seems like such a superior technology.

    It really makes me wonder how Noctua coolers manage to perform so well. Perhaps they just optimized every parameter of the heatpipes and manufactured the base and fin interfaces with extreme precision.

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