Posted by: drgeophysics | May 2, 2010

The bloop–loudest sound ever recorded on Earth: Source unknown.

NOAA Frequency Analysis of the Loudest Sound Ever Recorded on Earth.

The Bloop sound was repeatedly recorded during the summer of 1997 on the Equatorial Pacific Ocean autonomous hydrophone array over an area of 5000 km.  The sound 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. It yields a general location near 50 Deg S; 100 Deg W (far off the west coast of southern South America). The origin of the sound is unknown but too loud to be any know biological or living source.

The Bloop Wiki Page–an excellent place to start.

Here is an excellent site and the most detailed. Don’t worry about the x-files motif.

There are a series of unknown sounds that have been recorded in the oceans including: Julia, Train, Slowdown, Whistle and Upsweep.  Here is an excellent NOAA site where you can read about some of them.

As usual youtube has them also.



  1. that is freaky. hope that they figure out what it is… 😦

  2. Do they have any leads to what may have caused the “bloop”?

    • No, it’s a true mystery. My guess is that it is related to plate tectonic activity, but there is no solid
      basis for that. It is something truly at the frontier of knowledge. In this frontier, honestly, no one knows what is happening.

      The energy required for this noise is staggering, hence my thinking a tectonic/seismic/fluid displacement
      activity might be responsible. Again I stress, that is a thought, with no hard data to support it!
      The Bloop was well documented so there is no doubt as to the reality of the event.

      No idea really. Thank you for this comment. The answer is out there somewhere.

      • It is believed to be of biological origin, which is extremely scary to think of.

  3. It should be noted that, as the article says, the Bloop is the loudest sound humanity has accoustically recorded. However, the loudest sound in recorded history (as justified by seismometer readings) is the explosive eruption of an Indonesian volcano.

    • But when you think about it, the bloop was under water, which would require more energy from the initial sound. It is a lot easier for sound to travel through the air than it is underwater!

      • Perhaps; I am not a physics major or an engineer. I do know that sound travels faster in water than it does in air, as the momentum that (as you implied) it takes to get water moving (quite great compared to the counterpart in air) propels the wave outward quickly. So in that sense it is easier. One of many interesting things about the Bloop is (like many sounds recorded by the hydrophone array in question and hydrophone arrays in general) it was being conducted for such a long way by what is essentially a natural waveguide: A band of depth in the ocean where sound travels the slowest, as it is the zone of compromise between two trends: The increasing water density (pressure) with depth, and the thermocline, or temperature gradient, the farther one gets from the surface and sunshine. This lowest-speed zone acts like a fiber-optic cable, bending sound waves back into the channel when they stray towards the borders (Wikipedia has a good visualisation of this; essentially it is because the leading part of the wave goes faster, which kind of ‘turns’ the wave back into the channel [whose name, an abbreviation, escapes me currently…something like SOFAR]).
        Anyway, I guess it all comes down to how one defines volume. Density of wave peaks/troughs? Sheer mass or volume of matter moved? I think there is a pretty standard definition, so the answer is calculable.

      • Sound travels more easily through water

  4. The loudest sound ever recorded in “modern” history was Krakatoa. Where exactly were these sensors and how was it determined that the exact location of the sound origin was 5000km away? Were the sensors triangulated around the sound? Excuse my cynicism but researchers are always trying to find something new (which is a good thing sometimes). But, for all they know it could have been a rockslide 20m away. Now I am no geologist or physicist but I am a marine biologist. Those bloop sounds have low frequency that are definitely within the frequency range of whales. With that being said, the pitches are noticeably different to whales but point being it could still be biological. How loud was the sound? That would be a relative guess seeing how there is no decibel reading but looking at the frequency I would wager a guess from the human auditory range that it would be in the 55-130 db range. The one I can not account for biologically is the Julia sound. That one is erratic and doubtfully biological. What do I personally believe? I had to hazard a guess it would be tectonic activity if these sensors were in deep water. There is a plate with a handful of hot spots off the southern tip of Chile.

  5. […]…ource-unknown/ All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood. Reply With Quote […]

  6. And now it is a Mermaid? Could this really be true?

    • well they think it was cause by a mass of mermaids. 100-150 of them. Which would explain the volume of the sound.

  7. The loudest sound ever recorded was thunder from a positive lightning strike at a distance of 8 meters, with a magnitude of 712.7 decibels, by the University of Oklahoma. By contrast, the Tunguska blast of June 30, 1908 has been estimated at a mere 303 decibels.

  8. It was the earth itself moaning or crying out in pain

  9. 50 Deg S; 100 Deg W weird location kinda specific doesn’t seem random coulda been anywhere if it were something to do with sysmic activity i say uso someone checking out the ocean near Antarctica and i also belive it may be an animal of some sort one that was around millions of years before us and one that will be around millions after us i invision a predator that eats wales and from what i can find is that there is literaly hundrds of thousands of whales in antarctic and 15 differnt types of them are in the area i think a predator of a massive size something evan bigger than anything we thought could be there and doing quite well and be pretty full and we havent fount it cause it chills in antartica we spent alot less time there than we do anywhere else

  10. I still kind of doubt that the so-called bloop could outmeasure the 712.7 decibels of a positive-lightning thunderclap, as recorded by the University of Oklahoma.

  11. I was watching William Shatner’s Weird or What?
    This mystery noise of the bloop was examined as part of his great show.
    I believe the answer is too unbelievable.
    Could be natural more so than a military or beyond natural event.
    I can tell you that whenever I have heard ice moving on the lakes it makes a lot of different noises that are very difficult to describe. When I heard these sounds that the ice can make I can agree with Admiral Kirk. Weird or what.

  12. Could it be the left over noise of secret nuclear energy (weapons)?

  13. I adore this website – its so usefull and helpfull.|

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