The intriguing sound of marine mammals.

[Thanas]

TED talk


Very informative.

[Sea Skimmer]

Hmm, clear endorsement for atomic steam turbine powered merchant shipping. Diesels make more noise then anything else reasonably possible unless you mount them above the waterline.

[Thanas]

Well he did say that one is able to limit 99% of the noise by ship and propellor design....not sure how economical.

Also I was unaware of these huge hydrophones by the US Navy.

[Mr Bean]

Well he did say that one is able to limit 99% of the noise by ship and propellor design....not sure how economical.

Also I was unaware of these huge hydrophones by the US Navy.

Gotta hear those pesky Russian submarines somehow.
I'm listening to the talk now.

[Sea Skimmer]

Well he did say that one is able to limit 99% of the noise by ship and propellor design....not sure how economical.

It'd require rafting the machinery and covering it over with a physical sound proofed hood as is done on submarines, or else maybe you could do it using an active prairie masker which really requires gas turbine propulsion to be effective. Some surface warships have this, coats the hull in bubbles to physically reduce transmission of noise to the water. I'd also be skeptical you could keep one working for entire voyages, warships would normally only run them for days and not months at a time. Nothing that's going to do a 99% reduction is likely to be very reasonable but fairly large reductions, such as placing rubber shims on the engine mounts instead of a proper raft, might be fairly easy. Propeller design, I dunno about. The worst noise from propellers comes from cavitation and designers already do all they can to reduce that because it directly costs fuel efficiency.

I for one was just glad the whole talk was rational and didn't start blaming specifically USN active sonar for all the whale's noise problems, when a lighting storm is actually much worse in intensity and average duration. Took lots of lawsuit time before US courts accepted that fact.

Also I was unaware of these huge hydrophones by the US Navy.

Never heard of SOSUS? That's surprising. It was the worst kept secret of the late Cold War; though better kept was the secret that the reason they could function as far as 500nm offshore was because the US made them nuclear (RTG) powered. They run along both both US coasts at the edge of the continental shelf and across the GUIK gap, entry to the Bering sea and various points across the Mediterranean and English Channel. European powers and Japan and Russia more or less certainly have there own coastal waters wired for sound but far less is known about these, and they are more closely related to WW2 era harbor defense hydrophones everyone used then the deep ocean surveying capabilities of SOSUS. The first operational arrays were deployed around 1951-1952 and the project had direct British involvement from the onset, including use of British ships to install certain arrays to help conceal what was going on. Subs supposedly could be tracked traveling clear across the Atlantic, and any given station had over 1000nm effective range, with near unlimited detection range against noiser subs or surface ships. By taking bearings from several arrays you could get a fix on a target that was within a few nautical miles under the best conditions, more then enough to cue a surface ship or anti submarine plane. Such huge range, and hearing the whales is all dependent on something called the deep sound channel which is basically an underwater waveguide for sound. Sound doesn't travel massive distances through the ocean in a straight line, its far more bizarre.

SOSUS got declassified because it was so openly known by 1992, and because its hydrophones simply didn't work well on the latest Soviet submarines, nor could the survival of a fixed seabed system with cables to shore be assured in wartime in the face of numerous communist special operations submarines and direct attacks on the shore stations. Replacement was dedicated ships with massive towed arrays and deployable sea bed arrays, but the US saw no reason to suspend operations of existing SOSUS arrays since its a highly useful military sonar and civilian wildlife research tool. The Navy actually wants to know all it can about wildlife in the ocean because its vital to filtering out clutter and finding subs, a lot of existing research on this was declassified at the same time.

SOSUS was and is also used to find underwater earthquakes, the locations of missile and plane crashes into the ocean, and it was involved covertly with discovering the wreck of more then one submarine loss in the cold war including the communist K-129 and USS Scorpion.

[Adam Reynolds]

Well he did say that one is able to limit 99% of the noise by ship and propellor design....not sure how economical.

It'd require rafting the machinery and covering it over with a physical sound proofed hood as is done on submarines, or else maybe you could do it using an active prairie masker which really requires gas turbine propulsion to be effective. Some surface warships have this, coats the hull in bubbles to physically reduce transmission of noise to the water. I'd also be skeptical you could keep one working for entire voyages, warships would normally only run them for days and not months at a time. Nothing that's going to do a 99% reduction is likely to be very reasonable but fairly large reductions, such as placing rubber shims on the engine mounts instead of a proper raft, might be fairly easy. Propeller design, I dunno about. The worst noise from propellers comes from cavitation and designers already do all they can to reduce that because it directly costs fuel efficiency.

Slightly off topic, but regarding the bubble coating, was that the system that would appear on sonar as rain? I believe it was called Prarie/Masker.

Also wouldn't it be possible to defeat that system by checking the weather?

[Thanas]

I for one was just glad the whole talk was rational and didn't start blaming specifically USN active sonar for all the whale's noise problems, when a lighting storm is actually much worse in intensity and average duration. Took lots of lawsuit time before US courts accepted that fact.

Well, last I checked the US Navy is taking steps to avoid using sonar in active whale locations...though you gotta admit the difference between a lightning storm and an active sonar is one is man-made and the other one natural (and something they gotten used to). But yeah, global shipping is clearly far worse here.

Also I was unaware of these huge hydrophones by the US Navy.

Never heard of SOSUS? That's surprising.

I might have heard something about it, but not in great detail. I don't spend much time with sub warfare post 1945, really and before that it is more of a fleeting interest.

But thanks for the information, now I know more about it.

they are more closely related to WW2 era harbor defense hydrophones everyone used then the deep ocean surveying capabilities of SOSUS.

Were these panic installations after the Prien sunk the Royal Oak?

[Sea Skimmer]

Slightly off topic, but regarding the bubble coating, was that the system that would appear on sonar as rain? I believe it was called Prarie/Masker.

That'd be it. Invented by Canada I want to say? Or maybe it was the British.

Also wouldn't it be possible to defeat that system by checking the weather?

How is a submarine going to check the weather? I mean, it can go to periscope depth to do it but this is risky and only shows them out to the local horizon, maybe 10nm view and maskers are intended to work at fairly long ranges. Now while weather radio transmissions can be received while submerged they have limited bandwidth, and aren't likely to cover every rainstorm in an ocean basin, while highly specific weather reports for specific subs would, if intercepted by the enemy, possibly give the enemy an idea of the location of the sub. So basically its an issue of the shear scale of submarine and naval operations. Sometimes weather reports might work, other times they won't. parto f the issue is since you can hear sounds from all over the ocean, you'd be hearing lots of rain, and it would logically be harder to isolate that noise then very distinctive machinery noise.

Also part of the purpose of the masker was just to prevent the enemy from identifying specific ship types from the machinery and screw noise, and to aid the hunting ships own sonar by filtering out its own machinery noise with more generic noise. It is also useful for defending the ship against active pinging torpedoes, since the hull will no longer make such a good sonar target. Some diesel submarines themselves used the system to mask the massive noise of snorkeling.

[Sea Skimmer]

Well, last I checked the US Navy is taking steps to avoid using sonar in active whale locations...though you gotta admit the difference between a lightning storm and an active sonar is one is man-made and the other one natural (and something they gotten used to). But yeah, global shipping is clearly far worse here.

The lighting strikes are like 260 dB though, and strike tens of millions of times a year, against 215 dB for the loudest sonar which only pings once every several minutes when it happens to be operating. Most of the complaints about sonar were based on stuff that just wasn't true, mainly great exaggerations of how loud it really was which the USN did not correct prior to going to court because the data was classified.

Were these panic installations after the Prien sunk the Royal Oak?

No people began fielding them before the war ever began, and even back in WW1. Initially they were just tripwire systems with the hydrophones pointed straight up, then it was realized they could be used in more complex ways to target submarines crossing command detonated naval minefields. Then it evolved into systems which didn't just cross harbor mouths but narrow waterways and harbor approaches. Japan actually had hydrophones closing off all the entryways into the Inland Sea for example. another system was also used called an indicator loop, which was a magentic sensor loop. Such loops could not detect what part of the loop a submarine or ship crossed, just that it had in fact been crossed, but they could detect very quiet and small midget submarines. By layering several loops and hydrophone arrays you could build a pretty fool proof defense. Almost all, if not all, harbors entered by enemy subs in WW2 either didn't have these systems, or they were non functional or not being monitored at the time.

However until the deep sound channel was discovered in WW2 nobody thought you could make a passive hydrophone work at a range of more then a few miles. Ironically the initial work on the deep sound channel aimed to produce a system purely for search and rescue, by locating explosives triggered by downed pilots, but it worked so well they realized you could pick up ships and subs with it using large forward looking arrays. Once WW2 ended attention shifted to a longer term project to make this work for ASW leading to first full scale tests in 1951.

The panic reaction to Royal Oak was to build physical sea barriers, called the Churchill Barriers around Scapa Flow to replace the system of blockships Prien had defeated. Navies also came to realize you needed more then one layer of defense in general. Such as, if the RN had planted mines around those blockships Prien would have been screwed because a passage submerged was impossible, indeed it took both his diesel and electric engines running together to run against such a strong current. Fun project, it was completed just a few days before the war ended. The passages were thought to be blocked by tide and blockship, and so no indicator loops or hydrophones covered them. The main entryways to Scapa Flow did have that kind of defense as well as heavy nets that didn't have any gaps.
http://freepages.genealogy.rootsweb.anc ... rriers.jpg

Prien sailed through the closest channel in this picture. TRY THAT AGAIN!

[Thanas]

Thanks. Very informative, as always.