Sonar experts: How much sound crosses a layer?

[drEaPer]

Originally Posted by Wim Libaers

No, the reason for cavitation is not a chemical reaction where water decomposes (but chemical reactions might happen as a consequence of the high temperature reached when bubbles collapse during cavitation). It simply is that, at high flow speeds, pressure is reduced, so dissolved air will easily go out of solution, and water will boil at lower than normal temperatures. This is also why cavitation is less likely to happen when deep: the pressure is much higher, so (at the same temperature) you need a much faster flow to lower te pressure enough to start the boiling. It obviously also becomes easier with increasing temperature.

Of course, as soon as the bubbles come into a region of slower flow, they are not stable and will collapse. This is noisy and may damage the screw.

Thats what I said. Dunno how that chemical stuff comes up, I didnt say anyhting about that. I said mechanical (A spinning prop being the mechanical force creating a vacuum because the flow cannot keep up with the pace, therefore reducing the pressure which produces bubbles). My point was, that there is, and always will be air in h2O! Anyhow, thx for more input

[Wim Libaers]

Originally Posted by drEaPer

Thats what I said. Dunno how that chemical stuff comes up, I didnt say anyhting about that.

Actually, you did. Removing an oxygen atom from a water molecule would be a chemical reaction (one that isn't likely to happen though).

I said mechanical (A spinning prop being the mechanical force creating a vacuum because the flow cannot keep up with the pace, therefore reducing the pressure which produces bubbles). My point was, that there is, and always will be air in h2O! Anyhow, thx for more input

In water as it occurs in nature, yes (except perhaps in very hot springs), but it is possible to get the air out of water.

The "O" in H2O is not air, the air in water is just like the air we breathe, mostly nitrogen (N2) and oxygen (O2) plus some smaller amounts of other gases. This is dissolved in water, and goes out of solution when pressure is lowered or temperature raised. If you boil some water and see bubbles forming long before you reach the boiling point of water, that's dissolved air going out of solution. This is also the air that fish breathe (the O in H2O is not accessible for their metabolic mechanism), which explains why fish have problems in warm water: there is not enough dissolved air at elevated temperatures.

[LuftWolf]

Originally Posted by sonar732

Ok...let's not turn this into a flame war. Let cooler heads prevail until Jamie and/or Hutch addresses this issue.

Jamie and Hutch HAVE addressed this issue... it's called the Sound vs. Speed hotfix, which adds 5 Passive SL's to diesel/electrics and 10 Passive SL's to ALL nuke subs at top speed, regardless of make or max speed.

It's going to take a lot of convincing and solid evidence for me to think that what Amizaur engineered for the current LWAMI is not a better modelling job than what is in DW 1.00 or DW 1.01HF or DW 1.02/3.

Perfect. No. Linear. Yes.

Specific for each platform in a sensible way that contributes significantly to a good gaming experience, you bet.

So, it's not a finished product, and perhaps when we have more information about the thrust parameters, it can be made better, but what's in the mod now is a high fidelity and top quality database addition that makes DW a sigificantly better game and simulator, IMHO.

[sonar732]

Originally Posted by LuftWolf

Jamie and Hutch HAVE addressed this issue... it's called the Sound vs. Speed hotfix, which adds 5 Passive SL's to diesel/electrics and 10 Passive SL's to ALL subs at top speed, regardless of make or max speed.

It's going to take a lot of convincing and solid evidence for me to think that what Amizaur engineered for the currentl LWAMI is not a better modelling job and DW 1.00 or DW 1.01HF or DW 1.02/3.

Perfect. No. Linear. Yes.

Specific for each platform in a sensible way that contributes significantly to a good gaming experience, you bet.

So, it's not a finished product, and perhaps when we have more information about the thrust parameters, it can be made better, but what's in the mod now is a high fidelity and top quality database addition, IMHO.

By me saying let's let Jamie and Hutch address this is for them to explain the situation vrs. everyone who didn't write the code to go at each other's throats.

[LuftWolf]

Now everyone can see my typos.

I'm not sure that's going to happen... but we can try.

[LuftWolf]

OKO, I'm sorry but there is absolutely no increase of platform sound by speed in stock DW 1.0/1.01.

I have tried confirmation tests just now with the original database and it simply isn't there. (Not to mention the experience of many many players from the "early days")

In addition, if it were there, then the fundamental understanding of how the passive SL and thrust dialogues work in the DW modding community is fundamentally wrong.

I'm sorry, but stock DW 1.0/1.01 has no sound vs speed function at all.

[OKO]

So ... I don't know why I had this values ...
tested with all subs at that thime ...
anyway, as I already said, I don't care about older values, but about the new ones.
The debate is not to know if there was or not a sound gap on stock DW but to know why there is not on the actual values.

[moose1am]

Well I must agree ... here here! I am very new to this game but I have read over the last year all that I can find about how this game should work. I still have a lot to learn as this is a very complicated game if you really dig into everything. I found some information about sound layers and ocean environments and learned about layers, sound channels and how different ocean conditions Temp and Density caused by both temp and chemcial compostion of the water can effect the speed of sound waves. I use to play Subcommand a bit and tried to use the SSP buoy to figure out where the layers were located. I never really could figure out how the sonar worked in the different layers as I really didn't play the game very long.

But I sure am glad to see that someone is saying that the ocean environment is very important to determining how far or well you can hear an enemey ship in the distance on your passive and active sonar screens.

What we have is a lot of very important variables that effect sound wave propagations and that should effect the game play.

Depth and ocean bottom type are suppose to effect how the sound waves bounce around or change directions.

Being new to DW and even SC I sometimes wish that I could detect the enemy ships further away just to make the game more fun. When I first started playing Subcommand I went around never finding the enemy for long periods of time and finally tired of the game. I just put the game aside for a while but never forgot about it. I just told myself that I would get back to the game in the future. I just have so many other interests going on at this time that it's hard for me to dedicate too much time to this game. But time is what it takes to really learn this game.

I like the idea of reading the manual and or the tutorials and finding that the game works as described in the manual. As long as it's possible to figure out the game by reading how it's played I am going to be happy at this time. I like the idea of realism but I would not know what it real or not at this point in time. And as far as sound wave propagation most people have no idea on how it really works in the real ocean as it's not that easy to figure out. That is why this subject is classified in the real world.

I am just glad that someone said that there are lots more variables to this game that most people realize. We must not forget that when we complain about detection ranges so quickly. Not saying to stop complaining but to qualify your complaints with all the very important variables. Maybe there is a real reason why you can't detect somone out in the big blue ocean. From the deep blue to the litteral zones there are changing sea conditions that can effect what you can or can't hear.

Originally Posted by SeaQueen

Yeah... that's why I get really annoyed when people say things like, "the sonar ranges are too short [long]" and you never see anyone say what the SSP looked like, what season it was, what the seastate was, how deep the water was, etc.. The truth of the matter is that any estimate of sonar performance has to be qualified with an extensive description of the environmental conditions in which that performance was achieved.

Unfortunately, too often the only environmental qualification I see is that the detection took place in Tom Clancy land.

And if you really want to get into it, any good sonar model has to go hand-in-hand with a good global climatology.

In truth, outside of classified discussions, nobody really knows how good a given system will perform against a given target and that's how it should be.

[Molon Labe]

This started off pretty good, but this has gotten way off topic. I'm only asking about what sound propagation should be like in the real world and whether or not this is modeled well in 1.03. Specific performance characteristics of any sensor against any object is well outside the scope of this discussion. I doubt I'm asking for anything that's classified.

I think all this off topic speculation has turned away the people who have the answers sought.

And thanks, Bill! That helps a bit.

[SeaQueen]

Originally Posted by Molon Labe

The SSP effects are MASSIVE. It seems like even very loud sounds cannot be heard across the layer.

Are there any sonar experts that can comment on this? Thanks.

Whether sounds can be heard across a thermal layer depends on a lot of things.

In real life, even very strong ducts will leak energy. How much of that energy depends on things like the frequency of the sound. Sounds in the hundreds of hertz would require a surface duct so deep to be trapped that they simply don't occur. Even so, whether the energy leaked is enough to be detected depends on the sonar set, and how far away you are.

Also, as you get very close, you will receive direct path sound because the layer doesn't reflect sound as efficiently.

In real life there's also other interesting effects associated with fronts and eddy currents where sound leaks out of a surface duct because of changes in temperature across a front. A good example of where this sort of thing can occur is up around the Ryuku Islands northeast of Taiwan. There, the Kuroshio current spills lots of cold, salty, water over through the islands where it swishes around with the sub-tropical waters shallow waters on the shelf and all kinds of unpredictable things happen. These things have their biggest effect on medium and high frequency sounds.

So.... the answer to your question, in brief is "maybe, but not necessarily." Is this helpful?

[Molon Labe]

Yes, thank you.

[Hutch]

Originally Posted by OKO

let me give you a very good link about it :

http://www.fas.org/man/dod-101/navy/...P/snr_prop.htm

suggest you read that, than we continue talking about it
for our own culture and to know how to use it in DW

Figure 13 on that link is what's new in the patch. DW now traces that farthest-reaching ray that still penetrates the layer. Beyond that range, no detection. Up to that point, there's a slight range penalty for the curve of the ray, which usually results in a negligible signal loss. Note that those rays work in both directions- if you're hiding just above or below the layer, your cross-layer detections are going to be short.

[OKO]

very nice comments, Hutch.
We can see now strong effect on the sound propagation model.
experimented sub commander could take lots of advantage of this
thanx for this great improvment

On what you said, are we able to use the BD formula to find the shadow zone ?


and


?

[Driftwood]

EXCELLENT QUESTION OKO! I'm anxious to hear the answer to that!

[compressioncut]

Originally Posted by OKO

very nice comments, Hutch.
We can see now strong effect on the sound propagation model.
experimented sub commander could take lots of advantage of this
thanx for this great improvment

On what you said, are we able to use the BD formula to find the shadow zone ?


and


?

I don't mean to sound flippant but those formulas are painfully out of date, particularly if you are sub up against a towed array ship. The array can be placed anywhere in the water column.

Moreover, why would a sub captain want to do exactly what can be easily predicted? "Alright the layer depth is 70 meters, lets put the sub at 130m! The skimmers will never expect that!"

Presumably, it might work just fine against AI units.