A curious thought on DW passive sonar detection range

[Castout]

Yesterday when I played SC campaign in DW I noticed something that intrigue me:).
My platform was the Akula II Vepr and I played with LWAMI 3.08 mod installed.

With regard to passive sonar detection range I found that I was just able to detect an Arleigh Burke DDG travelling at 9-11 knots at about 3-3.5 nmi range which is roughly less than 7km away. And it only showed in the narrowband.

Now this is what intrigue me as when I played Silent Hunter III I found that I was able to detect slow moving merchant(5 knots speed) at about 10 km or more.

I know that with LWAMI installed I should have my passive sonar detection range enhanced and that DW is set in modern times when even the military surface ships are designed with noise dampening in mind hence they are more silent than merchant ships but my detection range for merchant ships is also not that great having able to detect them only at mostly 8 nmi(that is les than 12km) to have them on the broadband contact which enables the DEMON calculation.

I have also heard that DW only model direct sound contact but
Are these detection ranges not ridiculously too short for modern top of the line submarine?:hmm:

[To be]

Were you above or below the layer?

[Dr.Sid]

Here are some measurements I made. It is NOT detection range, but it shows pretty well how sound modelling is done in DW.

http://www.subsim.com/radioroom/showthread.php?t=117814

Edit: All hail new 'Ace of the deep, 1000 posts (and back safely)'

[sonar732]

When you post questions like those, it helps to provide us with information.


SSP
Where you were in relation to the world. ie...deep water, shallows, etc.

[Castout]

There was no thermal layer as I was in a relatively shallow water with the bottom at around 50-100m.

My depth ranged from periscope depth to 60 m.

[SeaQueen]

I have also heard that DW only model direct sound contact but
Are these detection ranges not ridiculously too short for modern top of the line submarine?:hmm:

The answer, ultimately, is that it depends. There are times a modern submarine might not detect something until it is a couple miles a away, there are times a modern submarine might detect something hundreds of miles away. You have to understand that the only major difference between an SQS-53 (today's high-end surface ship sonar) and an SQS-26 (shortly after WWII technology) was the composition of the sonar dome. The biggest advances have been in signal processing but even then, what the technological advances bought you, in practice was not always clear.

One of my pet peeves in submarine simulations is that people are always whining about what they think sonar ranges ought to be, and everyone mods things to reflect what they think everything ought to be in the abscene of any useful evidence or experience regarding actual sonar performance.

The truth is that sonar ranges are highly variable things that depend greatly on the minutiae of everything from whether the operator is tired or inexperienced, to small variations in the properties of the water column. Under some set of circumstances, you will can experience any sonar range.

In this light, the imporant thing from the perspective of a wargamer is not whether the range in game X is Y, and whether it is real or not, because basically any range is realistic for any sonars. Rather, the important thing is the tactics you develop to exploit or deal with the detection range you happen to get.

That's what real submariners do, and the point of wargames is to give you a taste of that. Each day, they use sophisticated computer models of sound in the ocean to attempt to get some feel for what it might be, and even that is subject to great uncertainty. There is no single answer to point to and say, "Ah Ha! that's the range for sonar X." I mean... in the sonar equation, the one of the most important terms is the recognition differential, which is simply to reflect operator skill and experience. I have read at least three papers arguing about how to actually compute it and they all have different opinions. I've also found inconsistences in identical conditions between pieces of software used to compute sonar ranges. Nobody has the answer. Sometimes they're big inconsistences. I remember one time I found a model that predicted that one got a convergence zone detection and in another they didn't. That's the difference between detecting at 35 miles and detecting at maybe 10 (on a good day).

Nobody knows how far their sonar can really see on any given day, at any given time. At best they can make educated guesses, which are frequently wrong.

There is no reason for submarine simulations to be consistent with one another. There is no reason for submarine simulations to choose any particular sonar range over any other. They're all correct.

I almost think the best way to handle things is to completely take any pretention of attempting to model underwater sound in the ocean out of the simulation and just draw it at random from some distribution. You'd probably end up with a result that was at least as correct as any painstakingly accurate acoustic model.

[Castout]

Hmm you have a point SeaQueen but I'm rather upset that I'm commanding a supposedly top of the line sub that could barely detect an enemy surface ship only at less than 4nm. I'm already blind now I'm almost deaf too:damn:.

Considering that in SH3 I could detect a merchant ship at much longer distance...

I know that I probably should treat 2 sims seperately but I just can't help myself comparing one with the other just to use one as a reference for the other.

But I do not mean to whine I just want a total revamp of the sonar detection range.....kidding:D

[sonar732]

I have also heard that DW only model direct sound contact but
Are these detection ranges not ridiculously too short for modern top of the line submarine?:hmm:
The answer, ultimately, is that it depends. There are times a modern submarine might not detect something until it is a couple miles a away, there are times a modern submarine might detect something hundreds of miles away. You have to understand that the only major difference between an SQS-53 (today's high-end surface ship sonar) and an SQS-26 (shortly after WWII technology) was the composition of the sonar dome. The biggest advances have been in signal processing but even then, what the technological advances bought you, in practice was not always clear.

One of my pet peeves in submarine simulations is that people are always whining about what they think sonar ranges ought to be, and everyone mods things to reflect what they think everything ought to be in the abscene of any useful evidence or experience regarding actual sonar performance.

The truth is that sonar ranges are highly variable things that depend greatly on the minutiae of everything from whether the operator is tired or inexperienced, to small variations in the properties of the water column. Under some set of circumstances, you will can experience any sonar range.

In this light, the imporant thing from the perspective of a wargamer is not whether the range in game X is Y, and whether it is real or not, because basically any range is realistic for any sonars. Rather, the important thing is the tactics you develop to exploit or deal with the detection range you happen to get.

That's what real submariners do, and the point of wargames is to give you a taste of that. Each day, they use sophisticated computer models of sound in the ocean to attempt to get some feel for what it might be, and even that is subject to great uncertainty. There is no single answer to point to and say, "Ah Ha! that's the range for sonar X." I mean... in the sonar equation, the one of the most important terms is the recognition differential, which is simply to reflect operator skill and experience. I have read at least three papers arguing about how to actually compute it and they all have different opinions. I've also found inconsistences in identical conditions between pieces of software used to compute sonar ranges. Nobody has the answer. Sometimes they're big inconsistences. I remember one time I found a model that predicted that one got a convergence zone detection and in another they didn't. That's the difference between detecting at 35 miles and detecting at maybe 10 (on a good day).

Nobody knows how far their sonar can really see on any given day, at any given time. At best they can make educated guesses, which are frequently wrong.

There is no reason for submarine simulations to be consistent with one another. There is no reason for submarine simulations to choose any particular sonar range over any other. They're all correct.

I almost think the best way to handle things is to completely take any pretention of attempting to model underwater sound in the ocean out of the simulation and just draw it at random from some distribution. You'd probably end up with a result that was at least as correct as any painstakingly accurate acoustic model.

:arrgh!::arrgh!::know::know::hmm::hmm:;);)

[sonar732]

There was no thermal layer as I was in a relatively shallow water with the bottom at around 50-100m.

My depth ranged from periscope depth to 60 m.

In another words...your sonar conditions SUCKED!

[Molon Labe]

Those detection ranges look about right for bottom limited in mud/sand, especially from PD. It's not just the Akula, all sonars are going to work like **** in ****ty acoustic conditions!

[Dr.Sid]

From my experience:

- AFAIK, in DW, shallow water does not affect sound travel, except for terrain blocking the signal. But I guess it should block everything or nothing, it should not weaken the signal.
- Sea state on the other hand does lower sonar performance significantly. So what was your sea state ?
- Burke at 10kts, at 3nm should be nice and bright, impossible to miss (based on my DW experience alone). There IS something fishy here, that is NOT normal. What array did you use ? What speed were you going ? All arrays are easy to washout with excessive speed. In shallow water towed array is easy to get draged on the bottom. Please post screenshots from that situation, from map and from sonar station.

[DrMilton]

Comparing SH3 with DW is not the right approach here. SH3's acoustic model is not so accurately designed as to include all the acoustic parameters that DW does. The Uboot's hydrophones will usually pick up contacts near their nominal "range" no matter what. Now, as a SH3 enthousiast myself I would gladly trade some of the aesthetic elements for a more accurate sonar environment and thus make hydrophone usage more fun. This is not to say that SH3 model is completely "flat" but it could sure be improved in terms of sound propagetion depending on SSP, sea state, ownship depth etc. Supposedly being near the surface makes it harder to hear contacts but I have yet to confirm that during play (although I try to convince myself that I have). Of course DW could in turn be improved in terms of ship's behavior on rough seas, masts that are invisible to the enemy etc.

Although both are great games some of their aspects cannot be directly compared so don't feel bad about not getting in DW what you would expect from SH3. Look at it this way: if you manage to master sonar in DW then no british ship will stand a chance against your uboot :smug:

[SeaQueen]

Hmm you have a point SeaQueen but I'm rather upset that I'm commanding a supposedly top of the line sub that could barely detect an enemy surface ship only at less than 4nm. I'm already blind now I'm almost deaf too:damn:.


Welcome to reality. Use your periscope, radar and ESM. That's part of why they're there.

[SeaQueen]

You really don't need a acoustic model to do WWII submarines because they were mostly relying on direct path energy to get their detections.

You need to know what's going on when you're dealing with bottom bounces, convergence zones and what not.

[DrMilton]

You really don't need a acoustic model to do WWII submarines because they were mostly relying on direct path energy to get their detections.

I presume that audible freqs behave the same as the rest of the freqs a modern sonar can pick up. So, if sound can't reach a modern sensor then it shouldn't reach the sonarman's ears too (...right?). A more accurate model would prevent this.

You need to know what's going on when you're dealing with bottom bounces, convergence zones and what not.

I'm not sure what you mean by that.

[Molon Labe]

From my experience:

- AFAIK, in DW, shallow water does not affect sound travel, except for terrain blocking the signal. But I guess it should block everything or nothing, it should not weaken the signal.
- Sea state on the other hand does lower sonar performance significantly. So what was your sea state ?
- Burke at 10kts, at 3nm should be nice and bright, impossible to miss (based on my DW experience alone). There IS something fishy here, that is NOT normal. What array did you use ? What speed were you going ? All arrays are easy to washout with excessive speed. In shallow water towed array is easy to get draged on the bottom. Please post screenshots from that situation, from map and from sonar station.

It's not the depth of the water that matters most, it's the SSP type. But, if the water is shallow, 90% of the time the mission designer will use the bottom limited SSP type. Once you're in BL SSP, there is a drastic difference between sonar performance based on bottom type; if rock it's almost as good as a surface duct, if mud or sand it's absolutely horrible. There is no middle ground.

Sea state does matter, but only by a mile or so. You could consider the SSP and bottom type the 'coarse adjustment' knob and the sea state the 'fine adjustment' knob.

[Dr.Sid]

Verified. Bottom type has major effects on sound travel in shallow water. I only did some simple tests. FFG, two surface targets at 5 nm and 10 nm. About 100ft depth.
Rock bottom gives nice signal, mud is worse, lets say double loss, half detection range.
Sand is disaster. Even FFG's own contact on TA deployed at 160ft gave just 2 lines ! 5nm target gave really weak 1 line, easy to miss. 10nm target was perfectly undetectable.
This calls for more testing, especially at what depth this 'shallow water mode' kicks in and if the transition is smooth or sharp.

[Molon Labe]

Verified. Bottom type has major effects on sound travel in shallow water. I only did some simple tests. FFG, two surface targets at 5 nm and 10 nm. About 100ft depth.
Rock bottom gives nice signal, mud is worse, lets say double loss, half detection range.
Sand is disaster. Even FFG's own contact on TA deployed at 160ft gave just 2 lines ! 5nm target gave really weak 1 line, easy to miss. 10nm target was perfectly undetectable.
This calls for more testing, especially at what depth this 'shallow water mode' kicks in and if the transition is smooth or sharp.

If by shallow water mode you mean an area near the surface where sonar performance is degraded.... This is something I've been wondering about for some time but never got around to really looking into. Some variables I suspect make a difference are the depth of the contact (not just location along the SSP as you've already documented, but also if they are located in the surface chop zone) and the sea state.

If you meant something that happens in areas of shallow water, then this is not something that I've observed but is still interesting if it plays out.

[Dr.Sid]

So i did some more test. And it's simple. Bottom type affects detection ranges in shallow water and deep water by same amount. There is no difference.
Sand will give about 30% detection range compared to rock even with few km of water under the keel.

Also my experience shows target depth does not matter, unless it crosses the layer. Depth of listener may affect detection ranges, if the listener is near surface, depending on sea state. With sea state 1, the noisy surface layer is thick few feet.

[Dr.Sid]

Yet one thing which decreases detection range. Extended masts. They create turbulence or so .. the increase in noise is visible in BB waterfall displays.
So with sand bottom, sea state 3, PD and masts out, such detection range seems to be normal (but then you did not tell your conditions with this detail).

[SeaQueen]

You need to know what's going on when you're dealing with bottom bounces, convergence zones and what not.

I'm not sure what you mean by that.

When sonars are sufficiently powerful that they can make bottom bounce detections or convergence zone detections then you need some kind of model of how sound travels in the ocean. In the second world war, from what I've read, they mostly only made direct path detections. If I recall correctly, the big advance of the SQS-26 over World War II sonars was that it could make bottom bounce and convergence zone detections.

If all one is worried about is direct path energy, though, then "cookie cutter" range laws are fine with detection.

[DrMilton]

If all one is worried about is direct path energy, though, then "cookie cutter" range laws are fine with detection. Yes, we're probably saying the same thing here. My point is that even a "range only" model should be more realistic and not allow contacts to be heard from 15 nm away no matter the conditions. Also, the inclusion of surface noise wouldn't be bad either.

[CapitanPiluso]

I like SH3 but I love DW
Nedless to say, but I always learn something new from you people and the excellent discussions in this forum.:up:

[SeaQueen]

Yes, we're probably saying the same thing here. My point is that even a "range only" model should be more realistic and not allow contacts to be heard from 15 nm away no matter the conditions. Also, the inclusion of surface noise wouldn't be bad either.

I could take it or leave it, honestly. In WWII sonar was so crude that it's not really clear how you would deal with much variability. Additionally, there was very little (if any) real attention to quieting. Everything was loud loud loud. That was an age where there were barely even industrial regulations on noise levels, let alone stealth considerations. You only really need to worry about the details of ambient noise or whatever else when the signal gets down near that level.

The Germans were the first to really start thinking about how to make their boats quieter. The innovations they sparked didn't really have an impact until after the war, though.

[DrMilton]

I can see that you have quite a strong opinion when it comes to people complaining about sensor accuracy or demanding more from the sim. Your arguments surely make sense and since I agree that having a tactical mind is the key to sims, I will leave it at that. :ping:

"In tactics, the most important thing is not whether you go left or right, but why you go left or right" A.M. Gray

[SeaQueen]

Well... the thing is... I'm not sure that including more and more details for the sake of adding details is giving you a better simulation. I suppose for a certain type of techno weenie it is, but I'm not that person.

The thing about all simulations is that their instructiveness tends to hinge on whether or not they capture the essentials of a given phenomena. My experience in both professional wargaming and in the hobby is that there is too much emphasis on including every little detail. None the less, as computers have become more powerful, it seems like the tendency has been to include greater and greater detail simply because the computational capacity is there. The thing is, I've spent many many days tweaking the knobs on these sorts of simulations with every gorey detail in them, only to discover that they didn't matter anyhow, usually for a good reason. A simpler model usually would have sufficed, and provided more insight more quickly. Often the values associated with the knobs in question are subject to such great uncertainty that it's questionable whether one can quantify their impact anyhow.

What I do wish they would do in computer simulations is make them more transparent. I'd really like them to say in the manual, "here's how we decided to model our sonar," for example. From what I can tell in DW, for example, it really just generates a very simple family of transmission loss curves, but it took someone else's experimenting to figure it out. If they made it more transparent, it'd be easier to figure out exactly what the scope of the model was, so one could make scenarios that were more challenging, given what it represents. I don't really care what assumptions they make so long as I know what they are and I can work with them.

I can see that you have quite a strong opinion when it comes to people complaining about sensor accuracy or demanding more from the sim. Your arguments surely make sense and since I agree that having a tactical mind is the key to sims, I will leave it at that. :ping:

"In tactics, the most important thing is not whether you go left or right, but why you go left or right" A.M. Gray

[Dr.Sid]

:yep:

[sonar732]

The only thing about that SeaQueen is, and I'm sure you're aware, is that if they even got a small fraction of anything classified in their sonar model the US Navy and any other nation they provided software for will have them for lunch.

This has been my stance eversince Sub Command and DW's early start. We don't know how much classified material they used for any of their modelling and can't make judgements as such.

[Dr.Sid]

DW sound simulation is deep in public area of knowledge. At the moment I could write the same simulation myself based of my measurements (although there may be details I missed, like recently discovered bottom type influence). I mean I could do that in a weekend, it really is simple. My sound propagation utility, based on public information (Ulric's book mostly) has all DW has (minus bottom) and much more.
Simply said .. sound propagation is public, including methods of simulation. Well maybe they have some super-simulation somewhere used for sonar design and so .. but DW is not in this class, by a big margin.
Classified things may be actual noise levels of ships, and sensor sensitivity, lets say 'parameters of actual military warfare' .. but that can be seen from the game itself.

Btw. don't get me wrong. Since 1.04 I think DW sonar modeling is more or less appropriate, considering how many receivers it can simulate in real-time (sonobuoy fields I mean).

[Dr.Sid]

Hm .. I thought about it .. why would I not make my sources public .. here are some reasons:

- I can't. Some contract does not allow that. For example I buy some module, I extend it, so it is crucial part of my new product. But I usually can't make public what I bought somewhere, even if I modify it.
Edit: also often when you do your project for someone (the navy), then use the same sources for other project (game), you are usually not allowed to make it public.

- I don't want to. For example I still use that code for my other projects, which I sell.
Also exposing your source codes is like exposing your soul. Also most source codes looks terrible and are far from 'how source code should look like', even in projects which are open source from beginning.

- I don't care. Making sources public .. why ? Will it make my name better ? Better than 'army contractor since 1973' ? Will it bring us more money, more projects ?
Isn't making naval simulation source codes public even in conflict with security policy of the state ? Should we risk it ?


Now all that could apply with SCS. Adding new playables would be little different. It could be trouble, if they plan to make DW 2. But if they don't plan (as I think), there is no reason for that anymore. They could allow that. Only difference would be that those mods, which exists I think, would be posted here, and would meet more audience.

[goldorak]

SCS could base DW 2 on a totally new codebase, keeping secret the core engine while at the same time providing modding tools for inserting new models, new database entries and why not a plugin architecture so that for instance the graphics engine is decoupled from the core naval engine.
Keep the secret stuff secret for their institutional customers, and let the game community have access to "public interfaces".
But this will never happen since all their games are based on the same old old old last century old code. :nope:

[DrMilton]

I don't see how something "classified" could be allowed to reach a commercial market, especially from a military contractor (who plays by the rules). It all looks more like marketing strategy or business arrangements between the companies that brought DW to the market (its not just SCS).

Instead of a conspiracy theory about secret hidden codes maybe we should just accept the fact that business decisions are made according to profit and government contracts are more promising than computer games.

So, just another product that gets abandoned. It has happened before.

[SeaQueen]

OH PUH-LEASE!!!! There's nothing classified in DW. If there was, everyone here would need a clearence, and your hard drive would be stored in a safe. You couldn't play DW over the Internet either, you'd have to use the SIPRNET. Oh, and the window behind your computer? You need to put some blinds on that. And nobody talk about the game, for heaven's sake without turning on the white noise generator! That'd be a classified conversation. People have been saying things implying that a given subsim contains classified information since Microsoft's Red Storm Rising. They didn't have anything then, and they don't have anything now.

Somehow, they draw on a small family of TL curves and use it to compute a very simple signal-to-noise ratio. There's nothing classified in that. Even the Navy's official sonar models are unclassified. At most they're maybe FOUO. The database feeding values into them is the classified part. Here's some screenshots of their sonar models:

http://www.d-a-s.com/imat.html

The only thing about that SeaQueen is, and I'm sure you're aware, is that if they even got a small fraction of anything classified in their sonar model the US Navy and any other nation they provided software for will have them for lunch.

This has been my stance eversince Sub Command and DW's early start. We don't know how much classified material they used for any of their modelling and can't make judgements as such.

[Dr.Sid]

OH PUH-LEASE!!!! There's nothing classified in DW. If there was, everyone here would need a clearence, and your hard drive would be stored in a safe. You couldn't play DW over the Internet either, you'd have to use the SIPRNET. Oh, and the window behind your computer? You need to put some blinds on that. And nobody talk about the game, for heaven's sake without turning on the white noise generator! That'd be a classified conversation. People have been saying things implying that a given subsim contains classified information since Microsoft's Red Storm Rising. They didn't have anything then, and they don't have anything now.

Somehow, they draw on a small family of TL curves and use it to compute a very simple signal-to-noise ratio. There's nothing classified in that. Even the Navy's official sonar models are unclassified. At most they're maybe FOUO. The database feeding values into them is the classified part. Here's some screenshots of it:

http://www.d-a-s.com/imat.html



Hmm .. this terrain influence sound propagation .. looks more interesting then I expected :hmm: I wonder if this could be done realtime. Will try, you know me ..

[SeaQueen]

Hmm .. this terrain influence sound propagation .. looks more interesting then I expected :hmm: I wonder if this could be done realtime. Will try, you know me ..

Sound in the ocean is REALLY complicated. People in video-game land don't always seem to realize it, though, because they have ray traces stuck in their heads of convergence zones, surface ducts, and bottom limited environments. The thing is, ray traces are not the best way to model sound in the ocean. They're only really good for relatively high frequencies and they don't really take into account things like interference.

What you really need to do is compute the normal modes of the parabolic equation. There's different algorithms for doing that. There's a book called Computational Ocean Acoustics which is all about just that.

Most of what you see on the web page is a graphical representation of transmission loss as a result of computing the normal modes of the parabolic equation.

As for real time.. it really depends on what you mean by real time. Once every few minutes? I think you could do that. I doubt you could use the parabolic equation for a video game, though. It would take a lot of horsepower. It'd be neat if you could, though. People would definitely find it a lot harder to estimate how far they could see because it could vary so much for no obvious reason.

[Dr.Sid]

Hmm .. this book is on google books . Awfully incomplete, as usual. You cost me a lot SeaQueen, you know that ? :rotfl:

Well I know raytracer is not enough. But I'm having troubles finding the differences. Let's say comparison between raytrace and other methods, on pictures, side by side.

For the game all this level is not needed. We just would use some of the features, like fluent changes (compared to steep changes), changes in time, sound channel, more effects of the bottom in active sonar, and some other stuff.

First we must select what effects are important and needed. Then we can talk about how to do it. I can do the later. I hope you SeaQueen will help me a bit with the former.

[Castout]

:doh:..okay.

Now can we enhance the passive sonar detection capability:rotfl:

[Molon Labe]

According to most publications, RL detection range is far shorter than in DW now. So, NO.

[Castout]

Really? I just tried a test with DW. This time a Type 42 DD at 2900 yards only shows up as thin line in 688i's normal BB. I went to NB to try to classify it and it was classified as either 2 torpedoes...weird.

In the end the DD detected me much faster than I did and launched 2 torpedoes at me missing me because I was too close.......

So I say most publications LIE:D. DD more quiet than a sub?

I have some screenies but too lazy to put them:rotfl:
I was travelling at 5 knots bottom at 9,000 somethin probably feet. No thermal layer.

[SeaQueen]

Hmm .. this book is on google books . Awfully incomplete, as usual. You cost me a lot SeaQueen, you know that ? :rotfl:

Well I know raytracer is not enough. But I'm having troubles finding the differences. Let's say comparison between raytrace and other methods, on pictures, side by side.

The biggest difference I've noticed is that raytracers tend to be pretty good approximations for TL in the thousands of Hertz range, and awful in the tens and hundreds of Hertz range.

There's also some lecture notes that go well with that book on MIT's OpenCourse website.


First we must select what effects are important and needed. Then we can talk about how to do it. I can do the later. I hope you SeaQueen will help me a bit with the former.

It's like I said, the phenomenta that are important are frequency dependent. The sonic layer depth might matter a lot for a sonar operating in the thousands of Hertz band, but have an almost immeasurable effect on a sonar that operates in the hundreds of Hertz. How to capture that in the game, is tough, though, because you'd have to solve the parabolic equations somehow (See the book I recommended).

[SeaQueen]

According to most publications, RL detection range is far shorter than in DW now. So, NO.

You know... back in the day, much was said about how sonar could detect things at ranges of hundreds or sometimes even thousands of miles. That's still true. The thing is, it all depends on the target and the acoustic conditions at the time. People don't like to believe that the really is that much variability but there is. In the '80s they were worried about hordes of NOVEMBER class submarines forcing their way through chokepoints in the northern latitudes, now they're worried about smaller numbers of KILO class submarines in tropical and subtropical latitudes. It's not that the sonars have changed, is that the environment and the targets have.

[Molon Labe]

Really? I just tried a test with DW. This time a Type 42 DD at 2900 yards only shows up as thin line in 688i's normal BB. I went to NB to try to classify it and it was classified as either 2 torpedoes...weird.

In the end the DD detected me much faster than I did and launched 2 torpedoes at me missing me because I was too close.......

So I say most publications LIE:D. DD more quiet than a sub?

I have some screenies but too lazy to put them:rotfl:
I was travelling at 5 knots bottom at 9,000 somethin probably feet. No thermal layer.

none of this information is any good unless you tell us the acoustic conditions, which sonar you're using, and what depth. And telling us what the filter classifies a contact is, is worthless with regard to sonar performance no matter what.

[Dr.Sid]

I said, the phenomenta that are important are frequency dependent. The sonic layer depth might matter a lot for a sonar operating in the thousands of Hertz band, but have an almost immeasurable effect on a sonar that operates in the hundreds of Hertz. How to capture that in the game, is tough, though, because you'd have to solve the parabolic equations somehow (See the book I recommended).
I found some more papers on the web, especially here:http://oalib.hlsresearch.com/PE
But man, this really goes beyond my math skills. In very very rough terms I understand what they talk about, but I'm pretty far from grasping the problem at the moment.

Will buy the book, anyway. It costs quite a lot, but I never regret buying Urick (which YOU made me to buy :lol:), which was not so cheap too.

[Dr.Sid]

After thinking about it I suddenly came to a theory what it's (I mean parabolic equation) all about and by looking on the formulas again it seems I'm right. I still will need lots of study, but at least I have SOME idea now. I'm also trying some very naive and rough wave based simulations. Which leads me to this: we really need just approximate what's going on. It means faking. For example if you say SSP has not much effect on low frequency, which means passive sonar, we can say OK, let's ignore SSP for passive. Level of the approximation is one thing. We can have simple methods, which will be frequency dependent, as well as complicated methods which wont. I'm trying to understand as much as possible, so I can decide 'this effect can be approximated by such and such simple curve, no need to simulation' or 'this could be simulated quite well, even quite fast, and it will help the game' or 'this is impossible to simulate or fake, and/or unimportant for the game, let's ignore it (but state in manual, of course)'.
It's not that frequency dependent effects are impossible or would require complex simulation. We don't need to be much true to the real world, we don't design real-world sonar set or something. We just need to catch the basic nature, the most important factors.

Which again reminds me one cool idea. Sonar is about listening right ? Even these days. Then why the hell does DW use few samples for all that boats and subs ? Why those samples are speed independent ? Why there are no transients ? It would be great fun to be able to HEAR: 'it's typhoon, doing lets say 10 kts .. ah ! changing depth now .. opening silo hatches !' Imagine tutorial missions teaching you to tell 2 screw from one and so on.

[SeaQueen]

I found some more papers on the web, especially here:http://oalib.hlsresearch.com/PE
But man, this really goes beyond my math skills. In very very rough terms I understand what they talk about, but I'm pretty far from grasping the problem at the moment.

The phenomena I descibed, where low frequencies aren't ducted but high frequencies are is described on p. 151 of Urick. Absolutely most basics of the normal mode theory (basically what the papers are getting into) for sound propagation is on p. 122 of Urick, although honestly, he really doesn't get into it there. He also does a little bit on p. 174. Urick, though, came from an era when ray-tracing was the general rule and computing power was limited. Now-a-days, computing power is significantly greater and so people parabolic equation models of sound in the ocean are favored. The results I showed you earlier come from parabolic equation models.

Basically, all of those models have different tricks for approximating the solutions to differential equations governing the behavior of a sound wave in the ocean given all sorts of complicated boundary conditions.

The bad news is, even though the models are very good approximations, the oceanographic data going into them typically isn't, so the output is still subject to great uncertainty. It captures a lot of phenomena that ray traces don't get, though.

Will buy the book, anyway. It costs quite a lot, but I never regret buying Urick (which YOU made me to buy :lol:), which was not so cheap too.

Urick is wonderful. There's just so much in there. Sometimes it's weird because every time I think there's something that's not in Urick, I end up re-reading it and realize that I was the dumb-dumb you had forgotten something, not him.

Don't buy a book you can't understand, though. I used to do that in highschool and didn't really catch up with myself until after I'd finished my undergraduate degree.

[SeaQueen]

I never said SSP had no effect on low frequency sound, just that the surface duct might not have much of an effect on it, depending on what the frequency is and what the duct depth is.


It's not that frequency dependent effects are impossible or would require complex simulation. We don't need to be much true to the real world, we don't design real-world sonar set or something. We just need to catch the basic nature, the most important factors.

That's fair, the thing is, it's sometimes hard to make a decision about what's important and what's not.


Which again reminds me one cool idea. Sonar is about listening right ? Even these days. Then why the hell does DW use few samples for all that boats and subs ?

Actually, in my experience, the sonar sounds in DW are pretty realistic for the boats and subs. That's what I remember them sounding like. It's basically just broadband noise.

Why those samples are speed independent ? Why there are no transients ? It would be great fun to be able to HEAR: 'it's typhoon, doing lets say 10 kts .. ah ! changing depth now .. opening silo hatches !'

I don't have any direct experience with this, but my sense of things is that the sonar operatator has a hard time telling how fast something is going just by listening. They might make a guess based on past experience, intelligence, or even just bound the problem by saying, "here's how fast he can go, here's how slow he can go," and judge from bearing rate, maybe. Doppler will give you a sense of relative motion and DEMON will tell you the speed, but I'm skeptical that a sonar operator can get much more than a vague sense of how fast something is going just from listening.

Transients would be a nice thing to have, but again, it's not clear to me how you'd do it. What would be the transient's source level? What would be their frequency? What about broadband transients? It all seems very hazy. You'd have to make a lot of assumptions about all the funny little pumps and motors and hydrolics that make a submarine go. I don't know what frequencies a hull creaks and groans at when it changes depths.

[PeriscopeDepth]

Anyone ever play Fast Attack? Had both transients and your sonar operator would call out "Contact Sierra 12 is changing depth!" Can't attest to how well it was implemented, but it was pretty cool.

PD

[SeaQueen]

Yeah... usually what they do is not worry about how the transient sounds or ends up on a lofargram, or whether or not the operator recognize it. Instead, they just assume that somehow they are detected, and then then have some kind of indicator that they are. Red Storm Rising also had them. Not for changing depths, but there were launch transients.

Anyone ever play Fast Attack? Had both transients and your sonar operator would call out "Contact Sierra 12 is changing depth!" Can't attest to how well it was implemented, but it was pretty cool.

[Dr.Sid]

Here's how i'd do it. I'd make sound effects first. Sound of pump. Sound of hatch opening. Something which is actually played in DW for the player to get the atmosphere.
Now all I want is that this shows on sonar too. BB and NB. I can do FFT of these sounds easily (and ahead), and for example ogg sound format which is used in OpenAL has in fact FFT analysis already done, only question is if I can access it. Anyway I did FFT before, it's no big deal.
Then also, of course, the transmission loss simulation (I mean approximation) must simulate how the frequencies are filtered. This filter must be applied on the FFT of the sound before displaying it on the NB screen, that is easy.
This filtered sound must be replayed into earphones, which too is possible and simple with OpenAL.
Like that you could let the enemy sub sing russian anthem, see it on NB, hear it in earphones, both affected by frequencies lost in underwater transfer.

As for the sonarman telling speed, yes, that was bad example, especially for the sub. Anyway I wanted to say that sub games these days don't model the sounds much well.
The sounds may sound 'correct' in DW. But the sound does not change with speed. There are only 2 or 3 sounds for all surface ships !

Look at IL2, the later versions. Engine sounds different for each plane. The sound is different from different angles. It is dependent on RPM, of course. Every damage to the engine can be heard. You got some hits .. then you LISTEN to the engine .. and you decide 'it sounds ok, I'll make it to the base !'.

And in IL2 it is mere sound effect. In subsim game this should be basic part of the game, I think.

[Hitman]

IIRC whales can communicate over huge distances, and they are basically just yelling in ultra low frequencies...

Seaqueen is right, given the proper conditions, anything can be possible :hmm:

[Dr.Sid]

I gave up on the parabolic equation. Anyway I created simple system for waves animation (I mean sea waves), and I found that it behaves well and that sound speed profile can be easily used with it. It has many problems and it's not suited well for sound simulation, but I could demonstrate few things. Check this out.

http://roger.questions.cz/other/wave/1.jpg

http://roger.questions.cz/other/wave/2.jpg

http://roger.questions.cz/other/wave/3.jpg

http://roger.questions.cz/other/wave/4.jpg

http://roger.questions.cz/other/wave/5.jpg

These shows sound propagation in sound channel with both bottom and surface reflection (in fact all borders reflects the sound, the right just a bit since the sound is weak there - it's one of the problems of this method, all borders reflects at 100%).

Frequencies are 4,8,16,32 and 64 pixels (size of the simulation is 100x500 pixels). SSP is very strong sound channel with axis exactly in center of the picture. It's completely out of scale, but it's wave-based sound propagation model and it shows how frequency affects things.

This actually animates the waves from the source, so you can see front-face moving through the medium and slowly (very) carving the shapes.

Anyway the best thing about this is I understand waves bit better now and I'm getting closer to understanding that darned parabolic equation :stare:

[Castout]

Ouch my head hurts :88)

[OneShot]

"Impressive ... most impressive"

[goldorak]

"Impressive ... most impressive"


You forgot http://content.answers.com/main/content/img/PosterThumbs/darthvader.jpg :rotfl:

[OneShot]

Right guy ... wrong picture. He said that when Luke jumped out of the gas freezing chamber :|\\ :know: ... but I'm digressing.

[goldorak]

Right guy ... wrong picture. He said that when Luke jumped out of the gas freezing chamber :|\\ :know: ... but I'm digressing.

Yes but I didn't find that scene sorry. :-?

[feld]

From my experience:

- AFAIK, in DW, shallow water does not affect sound travel, except for terrain blocking the signal. But I guess it should block everything or nothing, it should not weaken the signal.


Dr. Sid,
Have you ever been able to confirm that terrain blocks sound propagation in DW?
-feld

[feld]

According to most publications, RL detection range is far shorter than in DW now. So, NO.

You know... back in the day, much was said about how sonar could detect things at ranges of hundreds or sometimes even thousands of miles. That's still true. The thing is, it all depends on the target and the acoustic conditions at the time. People don't like to believe that the really is that much variability but there is. In the '80s they were worried about hordes of NOVEMBER class submarines forcing their way through chokepoints in the northern latitudes, now they're worried about smaller numbers of KILO class submarines in tropical and subtropical latitudes. It's not that the sonars have changed, is that the environment and the targets have.

Amen!

I want range & frequency dependent propagation loss !
@ SeaQueen : are there tabulated solutions to the wave equations? Dr. Sid might be able to use a lookup table?

-feld

[Molon Labe]

Quote:
Originally Posted by SeaQueen
Quote:
Originally Posted by Molon Labe
According to most publications, RL detection range is far shorter than in DW now. So, NO.


You know... back in the day, much was said about how sonar could detect things at ranges of hundreds or sometimes even thousands of miles. That's still true. The thing is, it all depends on the target and the acoustic conditions at the time. People don't like to believe that the really is that much variability but there is. In the '80s they were worried about hordes of NOVEMBER class submarines forcing their way through chokepoints in the northern latitudes, now they're worried about smaller numbers of KILO class submarines in tropical and subtropical latitudes. It's not that the sonars have changed, is that the environment and the targets have.


Amen!

I want range & frequency dependent propagation loss !
@ SeaQueen : are there tabulated solutions to the wave equations? Dr. Sid might be able to use a lookup table?

-feld
The DW acoustic model already has those.

The problem were up against as modders is that the acoustic model is outside of our reach. Unfortunately, we can only play with source levels and sensor sensitivity. So we have to choose a range of ranges within a fixed subset of what could occur in RL. I think they way things are now we've set the bracket on the high side of what might be the median, based upon publications and upon comments of submariners posted here. I'd be absolutely shocked if LWAMI ever acted shift that bracket higher (by "enhanc[ing] passive sonar capabilities").

[Frame57]

Hmmm! I wish I were a Sonar Tech, so I could add to this. But I was assigned to our 'tracking parties' while on the A-fish. We had no problems at all finding outbound boomers from the former Soviet Union. We would track em for weeks and make SSP's on them. I seriously do not think this game comes close to reality for many reasons. I cannot get a boat to perform anywhere near as well as our old cluncky 637 class boat did. It makes me wonder if they modled the sonar after paper cups and string attached to the hull. :nope:

[Molon Labe]

Hmmm! I wish I were a Sonar Tech, so I could add to this. But I was assigned to our 'tracking parties' while on the A-fish. We had no problems at all finding outbound boomers from the former Soviet Union. We would track em for weeks and make SSP's on them. I seriously do not think this game comes close to reality for many reasons. I cannot get a boat to perform anywhere near as well as our old cluncky 637 class boat did. It makes me wonder if they modled the sonar after paper cups and string attached to the hull. :nope:

Get in the editor and change the acoustic conditions. You can get a 2nd, maybe even a 3rd, CV contact on a clunky old boomer.

[Frame57]

Hmmm! I wish I were a Sonar Tech, so I could add to this. But I was assigned to our 'tracking parties' while on the A-fish. We had no problems at all finding outbound boomers from the former Soviet Union. We would track em for weeks and make SSP's on them. I seriously do not think this game comes close to reality for many reasons. I cannot get a boat to perform anywhere near as well as our old cluncky 637 class boat did. It makes me wonder if they modled the sonar after paper cups and string attached to the hull. :nope:

Get in the editor and change the acoustic conditions. You can get a 2nd, maybe even a 3rd, CV contact on a clunky old boomer.What! Me doing that is about as likely a filling in for the Neurosurgeon. :D

[Molon Labe]

Hmmm! I wish I were a Sonar Tech, so I could add to this. But I was assigned to our 'tracking parties' while on the A-fish. We had no problems at all finding outbound boomers from the former Soviet Union. We would track em for weeks and make SSP's on them. I seriously do not think this game comes close to reality for many reasons. I cannot get a boat to perform anywhere near as well as our old cluncky 637 class boat did. It makes me wonder if they modled the sonar after paper cups and string attached to the hull. :nope:
Get in the editor and change the acoustic conditions. You can get a 2nd, maybe even a 3rd, CV contact on a clunky old boomer.What! Me doing that is about as likely a filling in for the Neurosurgeon. :D
As I alluded to earlier, DW doesn't give you that many options to vary the acoustic conditions. It's not difficult. 95% of the variability is the SSP, and you only have 3 choices. It's a drop down menu, not brain surgery.

[Dr.Sid]

Dr. Sid,
Have you ever been able to confirm that terrain blocks sound propagation in DW?
-feld

Never tried .. and I can't try now since I don't have DW installed on my new notebook (but don't tell anyone).

As for us changing DW's propagation model .. it's hardcoded so forget about it.

[Molon Labe]

Dr. Sid,
Have you ever been able to confirm that terrain blocks sound propagation in DW?
-feld
Never tried .. and I can't try now since I don't have DW installed on my new notebook (but don't tell anyone).

As for us changing DW's propagation model .. it's hardcoded so forget about it.

In a simple line-of sight-way, yes. But I'm about 90% sure it doesn't do anything more complicated, for example, you can still get CVs in 500 feet of water even though the bottom should prevent that from happening.

[Dr.Sid]

Yes .. depth has no effect, that's sure thing.

[SeaQueen]

As I alluded to earlier, DW doesn't give you that many options to vary the acoustic conditions. It's not difficult. 95% of the variability is the SSP, and you only have 3 choices. It's a drop down menu, not brain surgery.

Maybe what we really want is not so much a real-time state-of-the-art sound propagation model, as the ability to enter real-life meteorological and oceanographic data from online databases, and use an off-line sonar model to generate a family of prop-loss curves to represent an environment that we've provinced off ourselves during scenario generation.

[Molon Labe]

As I alluded to earlier, DW doesn't give you that many options to vary the acoustic conditions. It's not difficult. 95% of the variability is the SSP, and you only have 3 choices. It's a drop down menu, not brain surgery.
Maybe what we really want is not so much a real-time state-of-the-art sound propagation model, as the ability to enter real-life meteorological and oceanographic data from online databases, and use an off-line sonar model to generate a family of prop-loss curves to represent an environment that we've provinced off ourselves during scenario generation.
Even if you had the outside database information, wouldn't you still need a high fidelity sound propagation model that utilizes that information during the simulation? Even if you could download data and plug that into the acoustic conditions of a DW scenario, you're still stuck with 3 low-fidelity SSPs and not many variables to use to tweak them. I'm not saying it wouldn't be a cool tool to have, but it seems like this would be a complimentary* improvement, not a substitute. Or am I misunderstanding the proposal?

*And one which would be a great feautre of a dynamic campaign engine! ;)

[feld]

Maybe what we really want is not so much a real-time state-of-the-art sound propagation model, as the ability to enter real-life meteorological and oceanographic data from online databases, and use an off-line sonar model to generate a family of prop-loss curves to represent an environment that we've provinced off ourselves during scenario generation.

Concur. Being able to define the SSP in "boxes" like the wind and current would be great. But we would be re-writing the DW SONAR model, I think, b/c it applies the same SSP over the whole 600 nm x 600 nm mission area. The new model would be the "range-dependent" proploss I referred to a few posts back.

Mission designers can work around this by choosing the SSP for the area where the preponderance of the ASW action will take place. That works ok as long as there's only one applicable SSP type. But this might not be the case, especially if the mission you're contemplating takes place over a large area, like a Theater ASW campaign or a Red Storm Rising-like convoy escort mission. The acoustic conditions in the littorals are also highly variable over large areas and so more "modern" naval missions involving submarines can be tough to do well.

-feld

[SeaQueen]

Even if you had the outside database information, wouldn't you still need a high fidelity sound propagation model that utilizes that information during the simulation?

The database is out there. You could just pull the water temperature and salinity from the Levitus climatology. There's also public domain bathymetry out there and that drives the pressure terms dictating soundspeed. There's lots so nice simulations available online.

Even if you could download data and plug that into the acoustic conditions of a DW scenario, you're still stuck with 3 low-fidelity SSPs and not many variables to use to tweak them.

I was thinking more of a future subsim other than DW.


*And one which would be a great feautre of a dynamic campaign engine! ;)

You know, back when Microprose's Red Storm Rising was out, I think they hit the nail on the head by limiting it's scope to the US/Soviet confrontation in one theatre. If you do that it makes it possible to do a lot more like that.

Falcon I think was very smart, because it did essentially the same thing. If you want to do something other than North Korea, you have to download a whole seperate campaign.

Harpoon is cool in that it allows you to do any conflict globally, but the thing about it is that it also has an easily extensible database, and is a lot more abstracted. The more detailed you make a simulation, the more limited in scope you need to make it in order to do a good job. I don't think it's wise to try to make a simulation all things to all people. It never works well.

If I was going to make a subsim, I would make it very limited and ONLY worry about a hypothetical US/China confrontation in the western Pacific in a single timeframe 15-20years in the future. It would also have a detailed database of US, Japanese, Taiwanese and Chinese warships. I might also add UK and Australian warships and land units. It wouldn't even attempt to have a global database.

Submarines would be the only playable platform. They would include 688i, SSN21, SSGN and 774 classes. I don't want to have to build a flight simulator or surface ship simulator on top of a submarine simulator. I'd want to make the controls of those platforms and the way they behaved underwater as correct as possible. There's also a part of me that wonders whether it might be fun to give players the option of going into the engine room and playing with the nuclear power plant where they could adjust control rods and manage the various radioactive decay products. It seems like the engineering section always gets short changed in these games. If you can take the helm, you ought to be able to man the throttles too.

The thing about naval sims, though, is that they're necessarily more slow paced than an air simulation like Falcon. Sub sims are particularly that way. An individual submarine's mission might last weeks. In light of that, I'm not clear exactly how dynamic it would make sense to make it because from the submarines perspective, minute to minute changes in the war don't matter much. It's more like the day-to-day changes. A scripted campaign would seem much more natural.

[Frame57]

I like campaigns where you "hunt". When we went on out "Northern" patrols we knew that was what it was all about. If we found a contact of Interest I am sure the CO had standing orders, but if it was something not is our profiles then we would radio it in and see what COMSUSDEVRON 12 wanted us to do with it. Sometimes Patrols I guess could be what you call scripted. Like testing out a new Sonar device or something like that, or testing ADCAPS impact on Ice caps etc... But to have a "fun factor" in these types of games I think havin unkown variables pop up is necessary. Else it gets boring reallly fast.

[SeaQueen]

Like testing out a new Sonar device or something like that, or testing ADCAPS impact on Ice caps etc... But to have a "fun factor" in these types of games I think havin unkown variables pop up is necessary. Else it gets boring reallly fast.

The thing about that sort of mission, is that even with random events thrown in, it gets old because ultimately you exhaust all the possible random events and the whole arguement that, "you don't know what's going to happen," goes away after you've played it a few times.

Really, in a wargame scenario, there's only so much "surprise" you can put into it. The trick is to figure out what randomness really drives the scenario and figure out how to put that in.

[Frame57]

Sure, at some point it will become the same ole, same ole. But the format of the SH series has some of that. When you make a contact is it going to be some old tankers with some escorts. Or will you find a nice big fat carrier or battleship to sink. Gotta love that. In modern times we do not have the history like WW1 and 2 to make these scenarios, but we could sure as heck make a fictitous one that would be awesome. WW3, we go against the Russian and Chinese navies using our 688i's and Virginia class boats and of course the few SSN 21's we have. I would buy it.

[SeaQueen]

Right now it's hard to imagine a plausible third world war. The name of the game is limited regional conflicts with specific political goals. This isn't to say you can't imagine some pretty big wars, but when you imagine the scenario you have to take that into account.

I mean... in WW3 losing a carrier wouldn't mean nearly as much as it would in a limited conflict where the American public might feel that the benefits of winning the war are outweighed by the costs in blood and treasure.

Sure, at some point it will become the same ole, same ole. But the format of the SH series has some of that. When you make a contact is it going to be some old tankers with some escorts. Or will you find a nice big fat carrier or battleship to sink. Gotta love that. In modern times we do not have the history like WW1 and 2 to make these scenarios, but we could sure as heck make a fictitous one that would be awesome. WW3, we go against the Russian and Chinese navies using our 688i's and Virginia class boats and of course the few SSN 21's we have. I would buy it.