Structural Micro-Drift Sentinel

Every wall and ceiling reflects signal with a timing fixed by its exact position — a millimeter of movement shifts the echo by a hair. One snapshot cannot see something that small, but weeks of patient averaging can. Slow creep in a joist, a foundation, or a facade panel shows up long before a crack does.

In the physics: A specular reflection off a structural surface has delay set by geometry to ~3.3 ps per mm of path change; super-resolved CIR delay tracking integrated over weeks can resolve slow displacement far below single-snapshot noise. Cracking/delamination also changes the layered-media reflection coefficient (amplitude/phase of that tap) even before gross displacement. Vibration modal frequencies of the element (Stage 2 band) shift when stiffness degrades.