Test Methodology
I use an LW-9266 Fan PQ performance measurement apparatus to evaluate cooling fans. This highly sophisticated scientific instrument was made in Taiwan by Long Win.
Fan Testing Machine Technical Specifications:
- Manufacturer: Long Win Science & Technology Corporation
 - Air Flow Rate: 2.4 – 250 CFM
 - Accuracy of Air Flow Rage: <3.5% INFS
 - Repeatability error: < 2%
 - Static pressure: 0-20mmAq (100mmAq with the high static pressure throttle device)
 - Overall Dimensions: 0.7 (W) x 2.2 (L) x 1.6 (H) m
 - Power Source: 220VAC, 5A, Single Phase, 50/60Hz
 - Based on Standards: ISO 5801-2007, AMCA 210-0, ASHRAE 51-2007, IEC 61591-2005, GB/T 1236-200
 
Besides the Long Win machine, I also use the following equipment.
Testing Equipment:
- Noise Test Environment: Hemi-Anechoic Chamber with 6 dB(A) noise floor
 - Conditions: 25 (+-2) degrees Celsius, 40-50% humidity
 - Sound Analyzer: Bruel & Kjaer 2270-S G4
 - Microphone: Bruel & Kjaer Type 4955-A
 - Mic Calibrator: Bruel & Kjaer Type 4231
 - Data Logger: Picoscope TC-08
 
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Tests show the white Silent Wings 4 140mm is noisier than the black version?
Epilogue
The high-speed version of the be quiet! Silent Wings 4 120mm
-> typo: should be 140mm
True.