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Comment by flir | Hacker News Reader

Or half the east coast. The implosion[?] of the ARA San Juan was supposedly heard 6000km away by hydrophones at Ascension Island. (https://www.ctbto.org/news-and-events/news/ctbto-hydroacoust...)

Or maybe they did and the data hasn't been processed/made public yet.

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Was interested by this comment and wanted to note a few things. The Titan is significantly smaller (in terms of length ~1/10th the size although obviously displacement is the real measure)[1][2]. And the depth of the implosion is about 4x deeper[1][3]. So there are things that could definitely affect the sound signature.

[1] https://en.m.wikipedia.org/wiki/ARA_San_Juan_(S-42)

[2] https://en.m.wikipedia.org/wiki/2023_Titan_submersible_incid...

[3] https://en.m.wikipedia.org/wiki/Titanic

Yes, and as far as I can tell it's not even certain that what was picked up from the San Juan was an implosion. But on the other hand, the Polar Prince was sitting right on top of the Titan listening for pings, and apparently it didn't hear anything.

I'm not suggesting anything nefarious, I'm just hoping someone who understands these things better than I do comes along.

Sound can bend in the ocean in weird ways.

The ocean is not a homogenous mass. As you go down you can measure temperature, pressure and salinity changes. These all individually and together affect the speed of sound in the water. Given the right circumstances a layer can form which bends the sound waves away from an observer. It is possible that they couldn’t hear the implosion precisely because they were on top of them. Perhaps they could have heard the implosion better if they were off to the side a few kilometers, or if they would have had a hydrophone dangling to the other side of the layer. More info on the layer. [1]

This perhaps also can explain why they routinely lost contact with the sub during dives. (And normalisation of deviance explains how they become okay with that. [2])

1: https://oceanexplorer.noaa.gov/explorations/sound01/backgrou...

2: https://en.m.wikipedia.org/wiki/Normalization_of_deviance

I'm speculating, but their ping detector may have had a filter for the frequency they were interested in. A low frequency explosion could easily have been ignored.

San Juan appears to have been about ten times the size of Titan, and that article says it took them over ten days to report the finding.

San Juan was 2300 tons and is made of metal.

Titan was 10 tons and mostly made of carbon fibre.

The size is irrelevant, the energy released is significant either way and definitely beyond the thresholds of hydrophones. During the USCG press conference today it was stated that the implosion made a significant soundwave as a result of the implosion, and I think in the coming weeks we'll hear reports of findings in regards to hydrophones which picked up the noise.

It also probably was armed with torpedoes when it was sunk, which probably detonated due to the explosive decompression.

> It also probably was armed with torpedoes when it was sunk, which probably detonated due to the explosive decompression.

I don't think that submarines explosively decompress under the ocean.

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