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NOAA (formerly unidentified)::List of unexplained sounds

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Sound::title    Sounds::pacific    Bloop::first    Source::recorded    National::large    Ocean::oceanic

NOAA (formerly unidentified)

Bloop

A spectrogram of Bloop

Bloop is the name given to an ultra-low-frequency and extremely powerful underwater sound detected by the U.S. National Oceanic and Atmospheric Administration (NOAA) in 1997. The sound is consistent with the noises generated by icequakes in large icebergs, or large icebergs scraping the ocean floor.<ref name=pmel1 />

Analysis

The sound's source was roughly triangulated to a remote point in the south Pacific Ocean west of the southern tip of South America, and the sound was detected several times by the Equatorial Pacific Ocean autonomous hydrophone array.<ref name=pmel1>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> {{#invoke:Listen|main}}

According to the NOAA description, it "rises rapidly in frequency over about one minute and was of sufficient amplitude to be heard on multiple sensors, at a range of over 5,000 km." The NOAA's Dr. Christopher Fox did not believe its origin was man-made, such as a submarine or bomb, nor familiar geological events such as volcanoes or earthquakes. While the audio profile of Bloop does resemble that of a living creature,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the source was a mystery both because it was different from known sounds and because it was several times louder than the loudest recorded animal, the blue whale.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The NOAA Vents Program has attributed the sound to that of a large icequake. Numerous icequakes share similar spectrograms with Bloop, as well as the amplitude necessary to spot them despite ranges exceeding 5000 km. This was found during the tracking of iceberg A53a as it disintegrated near South Georgia island in early 2008. If this is indeed the origin of Bloop, the iceberg(s) involved in generating the sound were most likely between Bransfield Straits and the Ross Sea; or possibly at Cape Adare, a well-known source of cryogenic signals.<ref name=pmel1 />

Julia

A spectrogram of "Julia".

{{#invoke:Listen|main}} Julia is a sound recorded on March 1, 1999 by the U.S. National Oceanic and Atmospheric Administration (NOAA). NOAA said the source of the sound was most likely a large iceberg that had run aground off Antarctica.<ref name=noaa /> It was sufficiently loud to be heard over the entire Equatorial Pacific Ocean autonomous hydrophone array. The unidentified sound lasted for about 15 seconds. Due to the uncertainty of the arrival azimuth, the point of origin could be between Bransfield Straits and Cape Adare.<ref name=noaa>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Slow Down

The spectrogram of Slow Down

{{#invoke:Listen|main}} Slow Down is a sound recorded on May 19, 1997, in the Equatorial Pacific Ocean by the U.S. National Oceanic and Atmospheric Administration. The source of the sound was most likely a large iceberg as it became grounded.<ref name="noaa" />

Analysis

The name was given because the sound slowly decreases in frequency over about 7 minutes. It was recorded using an autonomous hydrophone array.<ref name="noaa">NOAA page</ref> The sound has been picked up several times each year since 1997.<ref name="New Scientist">[1]</ref> One of the hypotheses on the origin of the sound is moving ice in Antarctica. Sound spectrograms of vibrations caused by friction closely resemble the spectrogram of the Slow Down. This suggests the source of the sound could have been caused by the friction between a large ice sheet moving over land.<ref name="New Scientist" />

Train

Spectrogram of the train sound
Spectrogram of the train sound

The Train is the name given to an unidentified sound recorded on March 5, 1997 on the Equatorial Pacific Ocean autonomous hydrophone array. The sound rises to a quasi-steady frequency. According to the NOAA, the origin of the sound is most likely generated by a very large iceberg grounded in the Ross Sea, near Cape Adare.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

{{#invoke:Listen|main}}


List of unexplained sounds sections
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