That’s the kind of detail that turns a plain corridor into a silent zone. On my runs I layer a low‑freq wash with a quick phase flip right after a sound source, then I keep a tight envelope on the output. The key is to stay in sync with the building’s own resonances—if you’re off even a fraction, the echo shows up. I run a quick scan pre‑mission to map the acoustic signature, then apply a counter‑mask that cancels the dominant modes. Keeps the footsteps from leaking and the enemy blind. How about you? Got a favorite frequency to pin on?