Noise Measurements
I turn on the sound meter Bruel & Kjaer G-4 Type 2270 15 to 30 minutes before starting the measurements to allow it to reach operational temperature. Before I start the measurements, I calibrate the sound meter using the Bruel & Kjaer Sound Calibrator Type 4231. I install the CPU cooler in the chamber vertically to the microphone, in a fixed position, to have the same conditions in each measurement. In all tests, the cooler’s fan(s) pushes air opposite from the microphone direction.
I utilize a Corsair Commander Pro to control the cooling fan(s), using custom software developed by me. In addition, the Commander Pro is driven by another passively operating system that doesn’t affect the chamber’s noise floor.
My software allows for precise fan sped adjustments in both RPM and percentage. Hence, I can set a portion of the speed individually for each fan, e.g., in a fan with a maximum speed of 1000 RPM, if I put 50% in the program, the fan will rotate to 500 RPM (±1%). I measure the noise the fan(s) produces at 10% – 100% of their maximum speed in 10% steps. Next, I change the fan speed by reversing the measurements’ logic to achieve 15, 20, 25, 30, 35, and 40 dBA noise output. I write down, of course, the corresponding speeds.
