Hush Wing Store — Quiet PC cooling: 80-140 mm | hushwing-store.com
A quiet 120 mm fan measures 18–25 dBA — and understanding the dBA scale turns that number into something you can hear in advance.
The dBA scale is anchored by everyday sounds: 0 dBA is the threshold of hearing, about 30 dBA is a quiet room at night and 60 dBA is normal conversation. Quiet 120 mm fans running at 600–1,200 RPM sit at 18–25 dBA, below the level of the night room itself.
Because the scale is logarithmic, each 10 dBA step sounds roughly twice as loud. A 40 dBA fan sounds about four times as loud as a 20 dBA one, so spec differences that look small on paper matter more than expected at a desk.
On narrow screens, swipe or scroll the plate sideways.
Speed drives noise more than any other single factor. The same fan is near-silent at 700 RPM and clearly audible past 2,000 RPM, where performance models commonly reach 30–40 dBA. Setting a PWM curve — a 25 kHz signal where 100% duty cycle is full speed — or lowering a 3-pin fan's supply from 12 V toward 5–7 V keeps it in the quiet band.
Bearing condition adds noise the spec sheet never mentions. A sleeve bearing past its 30,000–40,000-hour rating often rattles, while rifle and hydrodynamic designs (about 50,000–70,000 hours) and ball bearings (about 60,000–75,000 hours) hold their tone longer.
If a fan's real behaviour no longer matches its rating, the replacement guide walks through the swap step by step; if the choice is between frame sizes, the sizes guide compares airflow and hole spacing for all four standards.
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