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What made the loud unidentified sounds recorded by NOAA's Pacific hydrophones in the 1990s?

Asked 26 Oct 2026 by ·4 answers·0·0 following
Most likely: all of them are natural geophysical or cryogenic sounds (icequakes, grounding icebergs, volcanic eruptions…Ahead on the evidence, not yet confirmed. It needs two reviews to be accepted.

Where it stands

Four answers have been proposed. All of them are natural geophysical or cryogenic sounds (icequakes, grounding icebergs, volcanic eruptions… leads, with evidence 4 for, 1 against: partly supported by its tests. Three are still possible. Of the three narrower questions under it, none is answered yet.

Why it matters

The sounds were famous because they were unexplained, and the explanations now given rest on NOAA's own comparison of spectrograms and bearings rather than on published analyses of the original data⁠[1]⁠[2]. Whether the ice attributions hold is also a question about how much a single spectrogram and a bearing can prove, which matters for every acoustic anomaly that follows.

Answers 4

Evidence: 4 for, 1 against
Most likely
Evidence: 2 against
Disputed
Evidence: 1 for, 2 against
Disputed
None of these.
Not tested enough to call either way
Evidence: none yet
Still possible

History

  1. CNN puts forward: at least one of the sounds, most often the Bloop, was made by a large animal, known or unknown.
  2. Talandier et al.: ross Sea icebergs were recorded as far away as French Polynesia around the same years.For: All of them are natural geophysical or cryogenic sounds (icequakes, grounding icebergs, volcanic eruptions…
  3. CNN: the Bloop was far louder than any known animal; Lobel doubted cephalopods could make such a sound.Against: At least one of the sounds, most often the Bloop, was made by a large animal, known or unknown.
  4. CNN: the Bloop's rising frequency reminded biologists of animal calls.For: At least one of the sounds, most often the Bloop, was made by a large animal, known or unknown.
  5. Chapp et al.: ice tremor reaches estimated source levels near 245 dB re 1 µPa at 1 m and travels thousands of kilometres.For: All of them are natural geophysical or cryogenic sounds (icequakes, grounding icebergs, volcanic eruptions…
  6. Matsumoto et al.: antarctic icebergs are a major natural sound source heard at mid and equatorial latitudes, with seasonal…For: All of them are natural geophysical or cryogenic sounds (icequakes, grounding icebergs, volcanic eruptions…
  7. Asked on this site
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