Before radar, before satellites, we built ears out of concrete. Massive parabolic dishes were constructed along coastlines to catch the sound of approaching aircraft — primitive, patient, and entirely dependent on silence. A Passive Frequency extends this history into landscapes where it never existed: seismic vaults buried in desert plains listening for the tremor of a distant missile launch, hydrophone stations where cables once reached into the sea to monitor submarine movement far below. These structures share a common posture — concave, receptive, waiting. They represent a particular kind of anxiety: the fear that something terrible is already on its way, and that if you build something large enough, heavy enough, you might hear it coming in time.