Haha, unfortunately this stuff is complex ....Posted by panopticon (here)
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You've said there could be a difference in frequency due to the aquatic environment. How much of a difference could this make (not asking for a comprehensive analysis, the variations you pointed out make that ridiculous, rather just a general "lots", "not much" or "little")?
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Full info hereSpeed of Sound Underwater
While the accepted speed of sound in air is 340 m/s, the speed of sound underwater is more difficult to ascertain because the speed of sound is much more affected by temperature, dissolved impurities (usually salinity), hydrostatic pressure, and mass density. In an empirically derived formula, the speed of sound underwater in a simplified equation is:
C(T,P,S) = 1449.2 + 4.6T – 0.055T^2
+ 0.00029T^3 + (1.34 – 0.01 T)(S – 35) + 0.16z,
where is T represents temperature in ˚C, S represents salinity in parts per thousand, and z represents the depth in meters. More complex equations have been published, with the most accurate equation to-date involving 19 terms and coefficients up to 12 significant figures (7). Generally, an increase in temperature and salinity will increase the speed of sound in water. Usually, ocean salinity, S, is estimated around a constant 35 ppt, so the sound speed formula reduces to a function of temperature and depth, with the temperature of the water as a greater parameter than salinity. (5, 7).
So let me go by what I remember (for more simplicity sake) ... I think that practical values range between 1400 and 1500 m/s.
So a 6 .. 7 % variation is possible ... or said in a different way ... I would be surprised if they'd find an exact frequency of
37.5 KHz. But what else could be pinging in that area?
The reason why they hear it for a while and then it's gone is because they are moving ... it is possible that when you hear it
again you are actually further away. Have a look at the image below
This is about HF radio waves but the principle is the same ... the signal bounces up and down and can be received at
intervals where it reaches the surface .... You would need a powerful pinger though and I have no idea how powerful
these are but I would guess that with fully loaded batteries ranges of 10+ nm are feasible. Whales produce a much
lower sound and their range is therefor better. However the longer the range the more difficult it is to 'locate' the
source ....
Last but not least ... I expect them to find the pinger but most likely not the plane. Enough to satisfy closure of the
case but no answers on the question 'What happened ?'. But that is my intuition ... not based on intel or info.
P.S. They are most likely not listening at the surface but they are probably towing an array of hydrophones at a certain depth.






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