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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  • meacupla - Monday, February 7, 2022 - link

    If you are not aware, aluminum and copper have risen in price.
    Shipping costs are also based on weight and dimensions, so these heatsinks are also not favorable in that regard as well.
    Add in the fact that these passive heatsinks are a niche of a niche product, and probably not produced in such high numbers for noctua to get a substantive discount, and you end up with this price.
    In fact, as far as passive heatsinks capable of handling this wattage go, this is competitively priced.
    Reply
  • kgardas - Monday, February 7, 2022 - link

    You don't need to buy it. If rpi serves your purpose, then good for you! Reply
  • Wereweeb - Monday, February 7, 2022 - link

    Welcome to the world of niche products, where nothing achieves economies of scale, so everything is "expensive"!

    The only alternative for someone who needs this is making it themselves. Even just bending the heatpipes would stress me much more than paying $110 bucks.
    Reply
  • Einy0 - Monday, February 7, 2022 - link

    That's funny because I was impressed at how cheap it was compared to Noctua's other offerings. Premium products have premium prices. Raspberry Pis are literally designed from the ground up to hit ultra low price points. There is no comparison. Reply
  • grant3 - Wednesday, February 16, 2022 - link

    Is a raspberry pi 4b 8gb an effective cpu cooler?

    I'd think not; your comment makes as much sense as claiming a $30 oil change "seems steep" compared to a $2 can of tuna.

    Niche products sell in low volume no matter what, so the per-unit price has to be high to cover all the R&D, prototypes, custom machining, etc. etc. that a hardware business puts into designing a new product.

    If you think it is bad value, then fine, what is the equal alternative someone could buy for less?
    Reply
  • xenol - Monday, February 7, 2022 - link

    Randomness but I wanted to look up that Zalman case mentioned, but Google pulled up two other sites that basically plagiarized this site.

    Did I stumble into one of those places that recycles the internet for a quick buck?
    Reply
  • Hulk - Monday, February 7, 2022 - link

    I think the title of this review should have been "Silent but Deadly." Reply
  • GreenReaper - Friday, February 11, 2022 - link

    I mean, that's *one* way to win a deathmatch . . . Reply
  • kpb321 - Monday, February 7, 2022 - link

    This is one area where PC OEMs have the advantage if they choose to use it. They have the flexibility of modifying the case, mb, etc to all work together better and can do a much better job of channeling appropriate airflow over the needed components without having to resort to a bunch of small noisy fans. Generally only in the higher end work stations and such. They can be much quieter than a home built system would be even with those high power Xeon or Threadripper parts by using 120mm+ fans on the case instead of smaller fans elsewhere. Reply
  • Oxford Guy - Monday, February 7, 2022 - link

    Would be nice to see against the large and small NoFan products. Too bad that company is out of business. Reply

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