The Bloop
An ultra-low-frequency sound recorded across 5,000 kilometres of the South Pacific. It has never been explained by any known animal.
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Executive Summary
In summer 1997 the US National Oceanic and Atmospheric Administration's autonomous hydrophones detected an extraordinarily powerful ultra-low-frequency sound in the eastern equatorial Pacific. Nicknamed 'the Bloop' by NOAA researcher Christopher Fox, it was audible on multiple hydrophones separated by 5,000km — louder than any known biological sound. In 2005 NOAA proposed the sound matched an icequake signature. Some acoustic researchers remain unconvinced.
The Hidden Truth
What the headlines won't tell you
The Bloop is often cited in popular culture as evidence of a giant unknown marine animal. NOAA's actual position is more restrained: the acoustic signature is most consistent with a large icequake — the fracturing of Antarctic ice — but the sound-source location remains contested.
Case Timeline
- 1991-01-01GOVERNMENT RECORDSOSUS array declassifiedThe U.S. Navy's Sound Surveillance System network of Cold War-era underwater listening stations was declassified for scientific research use, enabling NOAA to access hydrophone data for acoustic monitoring.
- 1997-07-01PRIMARY SOURCEBloop recordedThe sound was detected by NOAA's Equatorial Pacific Ocean autonomous hydrophone array during routine acoustic monitoring, with the signal strength sufficient to register on sensors over 5,000 kilometers apart.
- 2002-01-01GOVERNMENT RECORDSound catalogued and namedNOAA researcher Christopher Fox assigned the nickname 'Bloop' to catalog the ultra-low-frequency sound event among other unidentified acoustic phenomena recorded by the hydrophone network.
- 2005-06-01GOVERNMENT RECORDIcequake explanation proposedNOAA scientists analyzing the acoustic signature determined its characteristics were consistent with ice fracturing events, proposing large-scale Antarctic icequakes as the likely source mechanism.
- 2012-11-01CREDIBLE REPORTINGNOAA formally attributes to icequakeNOAA publicly stated the Bloop's acoustic profile matched icequake signatures from Antarctic ice shelf calving events, though some researchers noted the source location triangulation remained imprecise.
Key People
Organizations
Evidence Library
- officialNOAA PMEL sound archive
The original hydrophone recording is publicly available on the PMEL website in both its native and sped-up form.
- documentDziak et al. iceberg-quake analysis
Peer-reviewed cross-referencing of Bloop and known cryogenic events in the Scotia Sea.
- officialNOAA FAQ attribution page
The agency's current public position on the source.
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Named in “The Bloop”.
Named in “The Bloop”.
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