Nucleated Self-Excitation Pass-Through: The Exchange Account of Two Kinds of Motion and the Pass-Through Spectrum

Transmissive behavior is the most individual signature of a medium, yet engineering has only attenuation coefficients, no mechanism word. Taking the self-excitation structure derived atomically in the companion paper as premise, this paper gives its display in field media: a wave is the self-excitation attenuation relay of a medium field—no spatial displacement; what is transferred is the self-excitation attenuation—and contends that the nucleation divide is an interface, not a wall: four pass-through channels and a bidirectional exchange account. The quantitative pillar is the inverse pass-through spectrum: 23 data points on a unified mean-free-path scale, spanning 21 orders of magnitude; class-level inversion holds strictly under the same-medium constraint; crossings are readings, not counterexamples. Solid-state pass-through gives the electrical isomorph (signal-drift duality, 10^12 speed ratio; superconductivity as the zero-attenuation limit). Closing: attenuation is the first ontological parameter of a medium. Companion data file: inverse pass-through spectrum, 23 rows.