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 & Conclusion
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  • Tom Sunday - Wednesday, February 16, 2022 - link

    I think with my other (total 6) rear, top and front case fans properly managed and active, that the NH P1 will be just fine for any required CPU cooling. With this I wish that passive cooling will be the future as anything mechanical and moving will always present problems and ongoing costs. Perhaps new and future chip development will ultimately reward us with cooling those not being required.
  • Spunjji - Wednesday, February 9, 2022 - link

    "You" in that sense would be a big chunk of this type of cooler's target audience. Moving parts are weak points, for sure, but having one 120mm FDB fan spinning at ~600rpm is hardly disastrous in that regard - and if your case has decent dust filtration at the intake, then you're probably going to get less of it on sensitive components than by having the sort of highly-ventilated chassis needed for fully-passive cooling.
  • Oxford Guy - Wednesday, February 9, 2022 - link

    Passive systems are less affected by dust.
  • Review - Saturday, February 12, 2022 - link

    Nice post
  • olde94 - Thursday, February 10, 2022 - link

    it's not a desktop but a laptop, but i use an older laptop with an intel y-series passively cooled CPU in my workshop as any fan would cause saw dust to fill the internal.
  • pSupaNova - Friday, February 11, 2022 - link

    Yes, I used to use the same too, now I use a Mac m1 Air as that has no fan.

    I think having a fan in a laptop is nearly as silly as putting one in a smartphone.
  • oleguy682 - Monday, February 7, 2022 - link

    Is the intent of this cooler to be used in a completely passive setup? Or is it relying on airflow from other components such as a case fan, PSU, etc? I ask because the Testing Methodology makes no mention of any kind of ambient airflow, which means this would be a worst-case scenario for the product. Even in a build meant to be nearly silent, there will be some kind of airflow. That airflow would add forced convection, which would do much more than the passive convection the test setup seems to provide.

    This product seems like one of those edge cases where an open bench test rig isn't going to come close to creating real-world results.

    Don't get me wrong, this is
  • fcth - Monday, February 7, 2022 - link

    Yeah, I imagine this is intended to operate with a case fan nearby drawing air across it. I actually have that setup in my HTPC, fanless heatsink on the processor (currently a i3-9100F, though it previously had an i5-2500k), but with two 120mm fans in the case so there's some airflow.
  • evilspoons - Monday, February 7, 2022 - link

    I can't find it right now due to a DNS problem making half the internet not work for me... but I seem to remember Noctua saying almost exactly that. It's meant to make a below-noise-floor PC, and having a tiny bit of airflow is important. This lets you use a big low RPM fan in an appropriate exhaust location.
  • kgardas - Monday, February 7, 2022 - link

    The intention of this cooler is of course to build fully passively cooled setup. I have one with W-2123 inside recommended (by Noctua) case and it runs w/o any other fan there. Yes, GPU is old, passively cooled too, but the machine serves its purpose...

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