The shift of sound energy from the first hundred entry halls to the second tier was not a simple linear progression across flat stone slabs.
Between Entry hall 100 and Entry hall 101 lay the Great Hydraulic Step—a huge upright popped joint in the Ark’s keel where the floor dropped eighty deep-water lengths into the middle cross-halls. In the original design of the vessel, this step had served as a main settling basin for river silt, equipped with thirty-six massive drain tube ducts cast from gunmetal bronze, each twelve arm-lengths in width. For twelve thousand years, these ducts had remained choked with hardened marine crust, dead bivalves, and dense, tar-like petroleum residue that had seeped from the sunken continents.
If the sound pulse from the Great Bell hit this blocked step without attenuation, the blast wave would reflect back into Entry hall 100. That created a sound water-hammer capable of shearing the bronze intake gates from their granite hinges. The resulting water-flow backwash would flood the lower refugee terraces with seventy feet of churning, gravel-laden salt water, drowning thousands before the water gates could be manually dropped. In the ninth cycle, that very disaster had drowned the southern refugee sector, killing forty thousand mortals in the space of three breaths. That was because the land-mapper of that age had neglected the phase lag of the drain tubes.
