Upsweep is an unidentified sound detected on NOAA's equatorial autonomous hydrophone arrays. This sound was present when PMEL began recording SOSUS in August, 1991. It consists of a long train of narrow-band upsweeping sounds of several seconds duration each. The source level is high enough to be recorded throughout the Pacific.

The sound appears to be seasonal, generally reaching peaks in spring and fall, but it is unclear whether this is due to changes in the source or seasonal changes in the propagation environment. The source can be roughly located at 54° S 140° W, near the location of inferred volcanic seismicity, but the origin of the sound is unresolved. The overall source level has been declining since 1991 but the sounds can still be detected on NOAA's equatorial autonomous hydrophone arrays.

Some of the other significant unexplained sounds named by NOAA along with Upsweep are Bloop

Bloop

The 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 in 1997...

, Julia

Julia (unidentified sound)

"Julia" is a sound recorded on March 1, 1999 by the U.S. National Oceanic and Atmospheric Administration . NOAA said the source of the sound was unknown, but sufficiently loud to be heard over the entire Equatorial Pacific Ocean autonomous hydrophone array. It lasted for about 15 seconds, and its...

, Slow Down

Slow Down (unidentified sound)

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 remains unknown.-Analysis:...

, Train

Train (unidentified 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...

 and Whistle

Whistle (unidentified sound)

The Whistle is an unidentified sound recorded by the autonomous hydrophone deployed at a location in the Pacific Ocean with coordinates. It was recorded on July 7, 1997. Origin of the signal is unknown, and it was not detected on any other hydrophone...

.

See also

• Bloop
  Bloop
  The 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 in 1997...
  
  
• Train (unidentified sound)
  Train (unidentified 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...
  
  
• Julia (unidentified sound)
  Julia (unidentified sound)
  "Julia" is a sound recorded on March 1, 1999 by the U.S. National Oceanic and Atmospheric Administration . NOAA said the source of the sound was unknown, but sufficiently loud to be heard over the entire Equatorial Pacific Ocean autonomous hydrophone array. It lasted for about 15 seconds, and its...
  
  
• The Hum
  The Hum
  The Hum is a generic name for a series of phenomena involving a persistent and invasive low-frequency humming noise not audible to all people. Hums have been reported in various geographical locations. In some cases a source has been located. A Hum on the Big Island of Hawaii, typically related...
  
  
• Slow Down
  Slow Down (unidentified sound)
  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 remains unknown.-Analysis:...
  
  
• Quackers
  Quacker (sound)
  Quackers are mysterious sounds, similar to a frog noise, widely reported by the crews of Soviet Navy submarines from various parts of the North Atlantic and Arctic Oceans during the peak of the Cold War, as well as their assumed sources...
  
  

External links

• Sound file of the Upsweep.