Datacenter · The edge of physics
Rack Row Vibro-Health: Failing Fans & Resonating Racks
People wish WiFi could hear a single failing server fan across the room.
We publish what we will not claim — that is how you can trust the rest.
Why the physics says no
Server fans spin faster than the vibrations WiFi sensing can read, and their casings tremble by only thousandths of a millimetre — too small and too fast for the signal to register. Big HVAC machines yes; individual server fans, honestly, no.
In the physics: Server fans and their chassis resonate at stable low-order harmonics; bearing wear and imbalance shift and broaden these spectral lines within the 0.1-40Hz structural-vibration envelope that phase-modulates RF paths reflecting off the rack faces.
Reviewer's verdict: Server-fan rotational and bearing frequencies (typically 50-200Hz+) lie above the stated 0.1-40Hz micro-Doppler band, and chassis casing vibration is micron-scale, which at 5GHz is well under 0.2 degrees of phase at range - below the CSI noise floor. Not observable (distinct from large in-band HVAC plant, which is separately plausible).