Acoustic Resonance Test

Morning illumination filtered through the iron grate overhead, cutting parallel bands of light across my subterranean redoubt. I advanced along the masonry ledge to test the acoustic fidelity of the vaulted brickwork. Clamping my mechanical claw around the discarded brass curtain ring anchored in the ceiling seam, I verified its immobility. Zero deflection occurred. I drew back my heavy spiked mace-fist and struck the exposed curve of the brass loop with measured force. A sharp, crystalline note tore through the humid air, echoing down the stone conduit before dissolving into the continuous roar of the culvert. The frequency was pure and unwavering. The lower vault retains absolute harmonic fortitude.