ColdChain Sentinel — refrigeration health from vibration signatures

A compressor's vibration shakes the signal at its own steady frequencies — a hum the mesh can feel. Worn bearings blur that hum, ice buildup drags it lower, and a door left ajar changes the load. Machines and people vibrate so differently that staff walking past never confuse it.

In the physics: Compressor and fan vibrations phase-modulate reflected CSI at their mechanical frequencies (10-40Hz and harmonics); bearing degradation broadens and shifts these spectral lines, icing changes load (frequency droop), and machine-vs-human discrimination is already proven so machinery lines are cleanly separable from staff motion.