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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  • plonk420 - Tuesday, August 8, 2023 - link

    love seeing my U14S on here as well as D15 in comparison. however, my U14S has really made me prefer the noise profile of 140mm fans. also, any chance of reviewing any Scythe coolers?
  • mode_13h - Tuesday, August 8, 2023 - link

    I think Scythe has fallen behind, over the past decade or so. Not that I would mind more cooler reviews and more data on the subject.
  • A5 - Tuesday, August 8, 2023 - link

    Their latest stuff (Fuma 2/3, etc) are at least competitive.
  • IlllI - Saturday, September 2, 2023 - link

    naw, the Fuma 2 is a beast
  • A5 - Tuesday, August 8, 2023 - link

    Yeah the U14S is a great cooler. Would love to see some of the new Thermalright products too.
  • andychow - Tuesday, August 8, 2023 - link

    Once you go Noctua, you don't go back to regular fans or coolers. They are just better, all around. And not in a flashy way. I've had Noctua fans running 24/7 since 2010, and they are still working, still silent.
  • Josh Mason - Wednesday, August 9, 2023 - link

    Agree. I got a Noctua that year and it was the best buy ever.
  • Jorgp2 - Wednesday, August 9, 2023 - link

    Conversely I've had consistent issues with my noctuas.

    PWM just stops working if the cable isn't just right
  • Samus - Thursday, August 10, 2023 - link

    I've had two air coolers in the last 15 years. They are both Noctua's, I still have them, and they are on modern platforms because Noctua sent out a kit to adapt my Socket 1366 cooler to Socket 1151, and recently sent the socket 1700 kit for my old D15. Free both times, no proof of purchase required (even though I had it.)

    Then there are their fans. The only fans I've ever owned that last a long time. I love Silverstone but the fans (especially the 180mm) has bearing issues and once the shaft completely separated from the fan assembly on my FT01. Even those cheap Noctua redux fans have worked well in cheaper systems I've put together like my IP CAM DVR in the garage and the kids' PC.

    Competition is great but I don't really know what it would take to get me to buy another brand of air cooler or fan.
  • escksu - Friday, August 11, 2023 - link

    Perhaps you have yet to seen brands like nidec, sanyo and delta....

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