工业双重低频撞击

Heavy industrial impact warning, 1100 ms. A deep 90 Hz struck-metal boom followed 300 ms later by a second, lower boom, with a rising metallic tension texture between them. Reads as an air raid actually starting. Clearly audible at a normal level, sustained across the full 1100 ms. Dry, weighty, mechanical. No reverb hall, no cinematic braams.