How are PC fan decibel ratings measured?
Almost always on a bare fan, at full speed, in open air, with no test standard named.
be quiet! labels its figures "at 100% PWM / 12V", and Noctua gives the maximum. Corsair breaks the pattern in a useful direction by publishing figures across its whole speed range, 10 to 36 dBA, the most complete presentation here.
Nobody publishes a figure for a fan bolted to a radiator or sitting behind a dust filter, and nobody names a test standard such as ISO 7779.
Two figures are only comparable at similar RPM as a result. The Silent Wings 4 140mm spins at 1100 rpm for its 13.6 dB(A). Noctua's NF-A12x25 spins at 2000 RPM for 22.6 dB(A) and moves air through much more resistance. In a real build they are not 9 dB apart.
Our 140mm case fan guide is built on that idea: it sorts every 140mm figure it could confirm by the speed it was stated at, and ranks fans only against others at the same speed. When two brands both skip the test standard, the result is figures that cannot be compared across brands, as the explainer sets out.
How do you make PC fans quieter?
Buy fans with more airflow than you need and run them slowly, through a PWM curve or the adaptor in the box. Makers that publish two figures for one fan supply the evidence.
| Fan | Full speed | Slowed down |
|---|
| Noctua NF-S12A | 17.8 dB(A) at 1200 RPM | 10.7 dB(A) at 900 RPM with the boxed adaptor |
| Noctua NF-A12x25 | 22.6 dB(A) at 2000 RPM | 18.8 dB(A) at 1700 |
| Phanteks T30 | 39.7 dBA at 3000 RPM, Advanced profile | 27.3 in Performance, 9.8 dBA in Hybrid, capped at 1200 RPM |
The NF-S12A loses 7 dB for 300 RPM. Corsair makes the same case for PWM control, which lets you set speeds so fans only spin as fast as they need to, and that means less noise.
Noctua's slowest models push the point further. Size for size they list lower full-speed figures than any pick here: 11.4 dB(A) at 800 RPM for the 140mm NF-A14x25 G2 LS-PWM, with 81.6 m3/h of airflow, and 6.8 dB(A) for the 120mm NF-S12B redux-700, which turns 700 RPM and moves 56.9 m3/h. The low figure arrives with low speed and low airflow.
Our Noctua fan decibels page lists every current Noctua fan and cooler by speed and adaptor condition.
Airflow fans for panels, pressure fans for radiators
What the fan pushes against decides which kind to buy. Open case panels favour airflow: Noctua's NF-S12A moves 107.5 m3/h at 1.19 mmH20, plenty for an intake or exhaust. Our PC case guide lists the fans each case ships with and their ratings, so you can see which are worth replacing.
Radiators and restrictive filters favour static pressure. The NF-A12x25 gives 2.34 mmH2O, the NF-A14x25 G2 2.56, and the thick Phanteks T30 7.37 mm H2O.
The usual mistake is a low-pressure fan on a radiator. It will not push enough air through the fins, so you turn it up, and then it is loud. Radiators come with liquid coolers, and our CPU cooler guide covers both air towers and all in one liquid coolers.
Mounts and gaskets ship in the box
Noctua includes anti-vibration mounts with its fans and packs a silicone gasket with the NF-A12x25 for radiator mounting, while the NF-A14x25 G2 arrives with the gasket already fitted. be quiet! supplies rubber and hard plastic mountings with the Silent Wings 4, though not with the cheaper Pure Wings 3.
On the design side, Phanteks keeps a 0.5 mm clearance between blade tip and frame to cut turbulence. Noctua quotes the same 0.5 mm for the NF-A12x25.
How long do PC fan bearings last?
From 80,000 hours for be quiet!'s rifle-bearing Pure Wings 3 to 300,000 for its fluid dynamic bearing Silent Wings 4. Those lifespans separate the price tiers more clearly than the noise figures do.
| Fan | Bearing | Rated life and warranty |
|---|
| be quiet! Silent Wings 4 | Fluid dynamic | 300,000 hours |
| Noctua | SSO2 | MTTF above 150,000 hours, six year warranty |
| Phanteks T30 | VAPO | 150,000 hours, six year warranty |
| be quiet! Pure Wings 3 | Rifle | 80,000 hours |
Five ways to misread a fan spec sheet
A 13.6 at 1100 rpm and a 22.6 at 2000 are not comparable.
Expecting the number on a radiator
Every published figure is free air. Expect any fan to be louder once it is pushing through a radiator or a filter.
Buying pressure fans for open panels, or airflow fans for radiators
Check mm H2O against CFM.
Ignoring the adaptor in the box
Noctua's costs nothing and drops the NF-S12A by 7 dB.
Assuming Sone means decibels
ARCTIC gives its P12 a rating of 0.3 Sone and prints no dB figure, so it cannot be compared with the rest. Our ARCTIC fan noise page sets out its sone ratings model by model.
