Upsweep: The Sound the Pacific Was Already Making When We Started Listening

2026-08-18 · True Mysteries Editorial Desk · Signals & Sounds · 8 min read

The sound was already there before anyone was listening for it.

In August 1991 the Pacific Marine Environmental Laboratory, a research arm of the United States National Oceanic and Atmospheric Administration based in Newport, Oregon, began recording from SOSUS. SOSUS, the Sound Surveillance System, was a Cold War asset: a network of hydrophones laid on the seafloor by the US Navy to track Soviet submarines by the noise of their machinery. As the Cold War wound down, parts of the network were opened to civilian science, and a small group of oceanographers suddenly had something no research budget could have bought, a continuous ear on an entire ocean basin.

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