The Bloop: The Ocean's Loudest Mystery and the Ice That Solved It

2026-06-18 · Signals & Sounds · 7 min read

In the summer of 1997, analysts at the Pacific Marine Environmental Laboratory in Newport, Oregon, part of the United States National Oceanic and Atmospheric Administration, were watching the slow scroll of spectrograms, the visual record of noise in the deep ocean, when a signal appeared that matched nothing in their catalogues. It was an ultra low frequency rumble that rose in pitch over roughly a minute, and it was extraordinarily loud. Hydrophones separated by more than 5,000 kilometres, an entire ocean apart, had recorded it at the same time. When technicians sped the recording up sixteen times to lift it into the range of human hearing, it resolved into a strange, wet, rising gulp. Someone called it the Bloop, and the name stayed.

The signal was not a single freak event. NOAA's acoustic monitoring programme recorded it several times during the summer of 1997 on the autonomous hydrophones of the Equatorial Pacific array, which is what allowed the analysts to triangulate an approximate source position rather than simply note an oddity on one instrument. The laboratory also made its stranger recordings public, posting the audio files and the spectrograms on its website alongside the whale calls and the seaquakes. That decision was ordinary science communication, and it is the reason the Bloop ever left the building.

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