Do I understand this sonar SSP stuff correctly?

[MarkShot]

I have read various documents on using the SSP information in the sub's sonar station.

I was just reading over Notfallmappe v6. It states that if two equivalent subs are listening for each other (assuming no layer) that the one located where sound travels fastest (fastest SSP) will have the best chance of detecting the other.

From my readings, I have come to understand that the opposite would be true. Due to the fact that sound waves are bent towards the slower SSP.

As I understand it:

(1) Sound waves are bent towards the slower SSP.

(2) Because of this bending behavior sound tends to travel into slower SSP water from faster SSP water and sound tends to not travel into faster SSP water from slower SSP water.

(3) Thus, if there is no layer or two subs are on the same side of a layer, then the sub in the slower SSP water has the better chance to detect the sub in the faster SSP water at some appropriate distance. (assuming equivalent subs)

(4) If there is a layer such that the water below the layer has the slowest SSP compared to water above the layer, then it is possible for a sub below the layer to hear sounds generated above the layer, but for sonar above the layer to be unable to hear sounds generated below the layer.

(5) If the layer itself should manifest the slowest SSP, then sounds which travel into the layer could be conveyed over an extended distance.

(6) If the layer itself should have the highest SSP, then this leads to a shadow zone where a hiding sub cannot be heard.

(7) Sound refracts in water in accordance to the SSP. Sound also reflects off the surface and the bottom. (This reflection is impacted by sea state and bottom type.)

---

My question is do I understand this stuff right? (every time I read something new I begin to wonder)

Thanks.

[MarkShot]

PING!

Where are all you experts and Navy veterans?

[Bellman]

:) Anyone not on holiday is lazing in the garden with ice cold drinks.
:lol: Taken me a week to get the message. (See Poll limits etc.)

Fish posted some excellent stuff from Blackjack of the Seawolves on the topics you raise. Sure a search will turn it up . :up:


Its 'Life gets tedious' time. :-j

[MarkShot]

The thing is that I have read those materials and other such materials. However, I am trying to see if I reached a simple and correct understanding. Hopefully, to be confirmed by someone with a deep and thourough understanding.

Thanks.

[Bellman]

:up: Good hunting - thats the 'Holy Grail' a ''simple'' understanding - I am still searching for the like -
on TMA, Scenario Design triggers etc.

My rather unsubtle point was that probably people just cant be bothered to muster the energy
and concentration to reply at this moment of time.

We shall see .

Cheers. :up:

[timmyg00]

Patience, friends...

I will try to answer the SSP questions tonight after work.

You guys are as bad as my customers... "I want an answer YESTERDAY!!"

;)

TG

[MarkShot]

There is just so much confusing and contradictory information out there.

For example, I have some of Blackjack materials printed out that explains how a layer need not be isometric and not act as a sound mirror - meaning that sound may propagate across the layer more easily from one side than the other.

However, I was reading Notfallmappe v6 today and in explaining the principles of ASW it notes that the layer is like a mirror trapping sound from crossing it either way.

So, my problem isn't so much lack of willingness or effort applied to understanding sonar passive/active concepts. Instead it is more like it is impossible to find a definitive and comprehensible source. A source from which a lay person could derive some basic and sound principles to be used as rules of thumb in game play.

Finally, of course, there is the issue of how sound propagation/detection is modeled in DW and SC (that's what I am playing) which may not necessarily reflect realworld behavior.

Yep, so, there is the SSP button with a nice little graph. I know it should be an aid to me, but either I don't know how to use this information or I lack confidence in what I think know.

---

Compared to WWII subsims the layer stuff was trivial. In SHI, you get below the layer and you are fairly safe and invisible at low speeds. Even without the bathythermograph, the resonance of pings changes dramatically as you pass through a layer. In SH2, you get this little announcement by sonar as you pass through. It diminishes the ease at which you are located, but not nearly as absolute as SH1.

Then you have SC and DW. I have had SC since it was originally released. I may be playing it five years from now and still be mystified by the "layer".

---

Timmyg00,

Perhaps now, that you are reknown for your "TMA for dummies/lay people/gamers"; it is time to move on to greater fame with "Active/Passive Sonar: Layers, SSP, seastates, bottom types and applying it effectively in SC/DW". :)

Thanks.

[MarkShot]

Oops! My mistake ... that was TopTorp who did the TMA thing. You wrote the SCHQ Tacman.

In any case ... all help is much appreciated.

[Dr.Sid]

This is how it works in real life. In DW the sound model is simpler. It is not exactly known how much simpler. There are some layer effects, but quite weak. I played many test missions and was helped by others just to find there is any SSP effect at all. Just do some test, you'll see.
What I found: You get weaker signal if you are on oposite side of the layer. The loss of the signal strength is 10% to 50%. Very occasionaly you can loose narowband line, in some very specific distance I think it is possible to loose contact, but it never happened to me. Most often layer does NOT change your ability to track or even identify.
Surface noise has much stronger effects. Shallow listener is affected by it and his contacts will be masked by surface noise. The noise reaches depths about 50m with sea state=3 and your detection range is several times smaller. You can completely loose contact which you have identified with 4 lines just few feet deeper. This is also main reason why deep sonobuoy has bigger range.
Surface noise effect is gradully stronger towards the surface. On waterfall display you can see lines gradually 'sink' in the noise while getting shalow. Layer effects in DW give sharp intensity change, and they occur EXACTLY on the layer depth.
While testing, note that towed array is usually in different depth then ship. If possible, use Sphere array to test SSP effects. Also note that on american subs narowband display you can see line fading away if the target changes bearing. Target gradualy moves to next bearing 'beam'.
This can be mistaken as SSP effect is bearing change is slow.

[MarkShot]

I was playing SCXIIc yesterday and engaging a Kilo with an Akula.

I had a very faint contact just good enough do TMA and DEMON. When it sped up (because I was shooting at it), I could easily track it above the layer. However, when it slowed to 3KTS, I would lose it on DEMON until I dove below the layer. I had that happen a few times.

[Bellman]

Taking up Dr. Sid's point I think near bottom turbulence, not TA related, is modeled well over certain surfaces.
Could be a passive torp beater in SC , but by no means infallible.

Also have witnessed the fading in and out of tonals in long distance duct 'boosting'. But cannot be sure
whether this is accurately modeled or just a feature of the variable (shades) receptivity, or water conditions, factored into the sim.

[timmyg00]

A couple of excerpts from the TACMAN:

MISCONCEPTION: Thermal layers will always hide you from an enemy that is
on the other side of the layer.
TRUTH: The thermal layer is not the “glass ceiling” or “magic shield” that many
players believe it to be.
This misconception springs primarily from the behavior of early PC
submarine simulation games, in which the acoustic environment was not as
accurately modeled as it is in Sub Command. Thermal layers in early sims
seemed to behave as a “glass ceiling”; signal strengths would drop significantly
as the thermal layer was crossed. This caused many players to believe that this
behavior is normal.

definitions:
· isothermal: little or no temperature change with increasing depth; leads to little
or no sound-speed change with depth
· positive gradient: speed of sound increases with depth
· negative gradient: speed of sound decreases with depth
· boundary: the depth at which two gradients meet, also known as the thermal
layer, boundary layer, sonic layer

From what I had read in FAS - used as a reference source for the TACMAN - wavefronts are refracted UP toward the shallows in a positive gradient, and DOWN toward the depths in a negative gradient. This indicates (and was reported by FAS) that the wavefronts are refracted towards water with a slower sound speed.

As to the original questions in this post:

(1) Sound waves are bent towards the slower SSP. Correct.

(2) Because of this bending behavior sound tends to travel into slower SSP water from faster SSP water and sound tends to not travel into faster SSP water from slower SSP water. Also correct.

(3) Thus, if there is no layer or two subs are on the same side of a layer, then the sub in the slower SSP water has the better chance to detect the sub in the faster SSP water at some appropriate distance. (assuming equivalent subs) Correct, although this should be qualified by citing the surface noise mentioned above; in a positive gradient, the sound waves are refracted up toward the shallows, where surface noise is greater. This indicates to me that there would be less benefit in lingering near the surface in a positive gradient environment in an effort to gain contact on a quiet submarine. On the other hand, in a negative gradient environment, there would be more benefit in going deeper to take advantage of the downward refraction.

(4) If there is a layer such that the water below the layer has the slowest SSP compared to water above the layer, then it is possible for a sub below the layer to hear sounds generated above the layer, but for sonar above the layer to be unable to hear sounds generated below the layer. This one is tricky. The environment in question would have a negative gradient on BOTH sides of the layer, with one gradient being sharper than the other (probably the one on the top). Not impossible, but I don't recall ever seeing it in SC or DW (not that it never happens, but that I just don't remember seeing it ;) ) However, if this environment existed, I'd say that this is largely correct - except that I'd replace "unable" with "less able".

(5) If the layer itself should manifest the slowest SSP, then sounds which travel into the layer could be conveyed over an extended distance. Correct. This is called a "sound channel", and is usually only seen at the boundary with the thermocline (not to be confused with thermal layer).

(6) If the layer itself should have the highest SSP, then this leads to a shadow zone where a hiding sub cannot be heard. Correct again; this is called a "surface duct" environment. However, in such a surface duct environment, one that produces a shadow zone where the wavefronts diverge, only very sharp gradients on either side of the layer will produce a shadow zone that acts like the "glass ceiling" mentioned above.

(7) Sound refracts in water in accordance to the SSP. Sound also reflects off the surface and the bottom. (This reflection is impacted by sea state and bottom type.) Correct. Rocky bottoms product the best reflections; reflection ("bounce") quality is less for a mud bottom, and worst for a sand bottom. As for surface conditions, I am guessing, but a calm surface should produce better reflections (as well as low noise), while a choppy or wavy surface produces scattered reflection and higher noise.

TG

[PeriscopeDepth]

(7) Sound refracts in water in accordance to the SSP. Sound also reflects off the surface and the bottom. (This reflection is impacted by sea state and bottom type.) Correct. Rocky bottoms product the best reflections; reflection ("bounce") quality is less for a mud bottom, and worst for a sand bottom. As for surface conditions, I am guessing, but a calm surface should produce better reflections (as well as low noise), while a choppy or wavy surface produces scattered reflection and higher noise.

TG

Is this how it is real life concerning bottom reflection? It's always struck me as weird that mud is better at 'bouncing' sound than sand.

Thanks

[MarkShot]

TG,

Thanks very much for your time to review and comment. I shall now sail forth with much greater confidence. (If only the crew would stop their infernal wispering when I turn my back!)

[Bellman]

:up: :up:

Nice little display Mark. Its called 'strutting your stuff ' ;)

Whens the write-up due ? If its half as good as your EAW stuff it will be a real treat. Looking forward to that. :)

[timmyg00]

TG,

Thanks very much for your time to review and comment. I shall now sail forth with much greater confidence. (If only the crew would stop their infernal wispering when I turn my back!) No problem. One thing I should have mentioned was that the shadow zone operates as much to hinder the hiding sub as it does to help it; if its sensors are within the shadow zone, it will be as blind to other subs as the other subs are to its presence.

And don't worry about the whispering. It's your navy, you can make your own rules, and bring back flogging to keep them in line.

TG

[XabbaRus]

Oh my head is spinning

You know I thought that if SSP is such that speed is increasing with depth then the speed of sound is slowest near the surface and faster deeper down and therefore I would have thought that the deeper sub would pick up the shallower sub cos the sound gets to him that little bit quicker...

I really need to read up on this.

Actaully what would be good would be a diagram for each condition

eg....Positive gradiet Sub A can hear better Sub B, Sub A can hid better.

Negative Gradier...same thing

etc and etc....

Always has been a headf**k for me...

[Bellman]

:) Good stuff - posted it up at 'Tips and Tweaks' with credits.

No doubt Landlubber will encompass it too.

Just give the crew 'chips with everything' but please no beans !
Mind with pay these days its 'caviar and...' ;)

[MarkShot]

Bellman,

Don't look to me for any materials ... with EAW I was an expert at online H2H ... I knew it and others did too. With SC and SCX, I wouldn't enter the water without a life guard on duty. :)

XabbaRus,

Part of the whole reason I started this thread is that in many discussions I have seen, the interpretation of the SSP is completely inverted.

In regards to the speed of sound in water, I think the issue of the SSP is not so much where might two sounds created at the same time and different locations be heard first due to the relative speed of sound travel ... refraction (bending) is the thing ... the issue is where the two sounds might be heard at all and the degree that the sound has attentuated or gotten lost in the background.

Interesting but OT note:

I was watching the History Channel regarding Civil War Combat. A particular segment was talking about how important sound was to battlefield commanders in terms of having a sense of what was going on. In particular, they were looking at the Gettysburg battlefield and how certain "acoustic shadows (as called in the ACW)" may have led to certain ill informed decisions during the battle. Remember that ACW battles had lots of smoke, since smokeless powder had yet to come into use.

[Bellman]

:) I would quite simply like to know from SS what layer features are actualy in the sim and how they are implemented.

The manual outlines three ocean environments claimed to be modeled in DW. (3 paras. just over a page)
Player observations seem to report patchy, irregular, sketchy and infrequent experience of any effects.
Possibly ths is real ? :o

If the effects are modeled then how ? Is it a Banquos ghost dice throw accompanied by variable water conditions ? :hmm:
What are the software mechanisms ?

It would be great if Jamie could take the chair and answer some of our questions. :up:

[timmyg00]

The manual outlines three ocean environments claimed to be modeled in DW. (3 paras. just over a page)
Player observations seem to report patchy, irregular, sketchy and infrequent experience of any effects.
Possibly ths is real ? :o Yes, I'd say that these reports reflect the ambiguity and random effects of a large fluid environment - much like our atmosphere. And when have you ever known meteorologists to be 100% accurate? ;) The SSP, and how sound will behave because of it, is not predictable to the degree that it will always do what you expect.

TG

[Bellman]

:) TG,

Thanks - I will take that to mean then that you as an ex-officer accept that the sim is reasonably 'realistic' in this area. :up:

[Dr.Sid]

I tested a lot yesterday. I was trying to test how deep goes the surface noise. I found several things: you can set sea state to 0, which leads to absolutely quiet sea. You can see contacts at great distances and there is no noise on waterfall displays AT ALL, unless you go too fast. Very interesting (very unrealistic, bug good for some types of tests or training).
The difference between surface noise at sea state 1 and seastate 5 is quite small when you are deep. Wilder seas makes surface noise go deeper. At seastate 5 I started to see effects about 350ft (just where the layer was), at seastate 3 about 150 ft, seastate 1 is hard to say, but it is quite shallow. It affects you in PD but then it dropes quite fast.
The layer effectivnes (I tested it too) seems to depend of 'steepnes' of SSP. Several times during this testing I was able to really loose NB lines with sphere sensor. I was moving on the border of detection range. Sometimes there is only very faint darkening on NB lines.
I was even once able to see layer effects on BB display ! It happened with seastate 1, so there was not there was not much noise in layer depth. I had 2 lines on NB sphere sensor. After crrosing th layer I lost the higher line and the other got very dark, it almost vanished too. On BB, you could see line getting thinner on slow display. On fast display, the already very thin line vanished !
All these changes happens instantly in the moment you cross the layer depth. Surface noise changes gradualy. Layer effects are wasy to see only on faint contacts. You ususaly get not SNR change, because it is 0 all the time.
There are also other noises .. sensor washout, noise from extended masts, noise from opened tube doors, noise fro explosions .. all these can make your contacts weaker, so watch out !
SSP in DW can't be exactly reproduced. You only set SPP type (all test was made with convergence zone), but the depth of layer (and maybe steepnes) is random.

[Bellman]

:) Interesting test results and thanks for sharing them. :up:

I think given software limitations we have to accept clean cut offs and randomisation. I have observed the fading
tonals and sometimes an exciting experience where you get a fleeting mirage like glimpse of long distance
tonals swithching on and off with SSP performance. :cool:


If the long range hearing bug cant be fixed in a patch perhaps the game balance could be restored by
increasing the subs baffle areas ! And/or stopping the feature where torps explode on CMs !! :hmm:

[timmyg00]

which "long-range hearing bug"? :hmm:

TG

[Rip]

(7) Sound refracts in water in accordance to the SSP. Sound also reflects off the surface and the bottom. (This reflection is impacted by sea state and bottom type.) Correct. Rocky bottoms product the best reflections; reflection ("bounce") quality is less for a mud bottom, and worst for a sand bottom. As for surface conditions, I am guessing, but a calm surface should produce better reflections (as well as low noise), while a choppy or wavy surface produces scattered reflection and higher noise.

TG

Is this how it is real life concerning bottom reflection? It's always struck me as weird that mud is better at 'bouncing' sound than sand.

Thanks

Sand is rough and porous reflecting the sound waves at different angles. Ocean mud is smooth and flat, although it doesn't take much for something with mass to disturb it sound reflects very well off of it. Actually better than some hard bottoms that are rocky or unflat. Mud is almost always nearly flat.

[Dr.Sid]

[quote="timmyg00"]which "long-range hearing bug"? :hmm:

At least Kilo and MH60 sonar can hear contacts at unrealistic distances.

[Bellman]

TG, Kilo BB is over- efficient is'nt it ?

My 'long -range hearing bug' was vague. :yep:

[OKO]

TG, Kilo BB is over- efficient is'nt it ?

My 'long -range hearing bug' was vague. :yep:

not BB, only cylindrical BB, the conformal looks clean

[Bellman]

:yep: :) :up:

[Fish]

TG, Kilo BB is over- efficient is'nt it ?

My 'long -range hearing bug' was vague. :yep:

Don't start a chat with my wife about me hearing. :down:

[Bellman]

:lol: :up: Fish.

' I did'nt hear you' is always my first line of defence. ... Cuts out a lot of 'chores' ;)

'Sans teeth,sans.....' Once you hang up your boots its all downhill - so the frigging pessimists say. :hulk:

Dont accept that. :arrgh!: :damn: .........................................Yet :-j

[Kapitan]

Akula II her towed sonar is pretty good but then her normal sonar isnt bad could be better oh well i dont mind just as long as i can track things

[Bellman]

:D Fish,

Coincidentaly regarding our ear 'problems' there is an article in my paper today entitled -

'Sorry dear did'nt quite catch that !' (Basil Fawlty) And its because we are not on the same wavelength.
'Its one thing gauranteed to madden a woman - her man not really listening when she's talking '

'But it might not be simply down to rudeness (sic) Research has revealed that the way men are wired
for sound means they find female voices more difficult to understand than male voices.'

'Research in the US has shown women use both sides of the brain to listen, while men only use the left side'

So you see Fish we have baffles and we know the art is to put 'em at the wifes bearing.

I have printed out a copy of the article for mine and she feels very superior . However I omitted the bit
which went on to say - 'However previous research has shown men think faster than women -
and so could have the intellectual upper hand. '
Note the could !! :roll: :o :huh: :arrgh!:

''Sorry dear I did'nt quite catch that......'' ;)

[Fish]

:D Fish,

Coincidentaly regarding our ear 'problems' there is an article in my paper today entitled -

'Sorry dear did'nt quite catch that !' (Basil Fawlty) And its because we are not on the same wavelength.
'Its one thing gauranteed to madden a woman - her man not really listening when she's talking '

'But it might not be simply down to rudeness (sic) Research has revealed that the way men are wired
for sound means they find female voices more difficult to understand than male voices.'

'Research in the US has shown women use both sides of the brain to listen, while men only use the left side'

So you see Fish we have baffles and we know the art is to put 'em at the wifes bearing.

I have printed out a copy of the article for mine and she feels very superior . However I omitted the bit
which went on to say - 'However previous research has shown men think faster than women -
and so could have the intellectual upper hand. '
Note the could !! :roll: :o :huh: :arrgh!:

''Sorry dear I did'nt quite catch that......'' ;)

Can I have a copy please? :lol:
I like here to think she is superior. :up:
Now she wants me to go to the hospital for a hearing aid. :roll:

[Bellman]

:lol:

Link:- http://www.dailymail.co.uk/pages/live/articles/health/menshealth.html?in_article_id=358320&in_page_id=1800

If its pulled as its a daily - pm me and I have a copy which I will send to you.

Considering putting up a copy on our message/reminder board - strategicaly placed in the 'demilitarised zone.' :hulk:

Good luck in the 'War of the sexes' :arrgh!:

I have occasional days when I 'think' I am winning. :-? :roll: :huh:

[Bellman]

:damn: :damn: :damn:

See what I mean - these women dont play fair - the bit I posted which is vital and a 'golden bullet'
for our campaign has been dropped :down: :hulk:

''However previous research has shown men think faster than women - and so could have the intellectual upper hand. ''

You see that sides 'Gatekeepers' are everywhere the (Female) editor has wiped that bit from the internet precis !! :arrgh!:

I will pm you this ace card ! :cool:

Good luck - keep chipping ! :rotfl:

[Bellman]

Why keep it private - heck theres a lot of us struggling out there.
The lost majority - guys plugging away to keep the edge.

We need some solidarity and in the interests of 'openess' this stuff is dynamite -

' Earlier research inthe US showed women use both sides of their brain to listen, while men only use the left side.

Dr.Joseph Lurito, ofIndiana University said ''Studies suggest women can handle two conversations at once.
Maybe they have more brain devoted to it.''

However previous research has shown men think faster than women - and so could have the intellectual upper hand.
Scientists who measured the speed at which messages passed along brain cells discovered that
men were 4% faster (WOW) at transmitting impulses between cells than women.

The Canadian study tested nerve condition velocity , the speed at which impulses are conducted along nerves by the brain.

Researchers concluded that the men's faster responses were down to the nerves in men's brains having a thicker
coating of myelin, a fat-based material which protects nerves and improves conductivity.

Article by Fina MacRae Science Reporter, Daily Mail UK. 6/8/05.

Ms MacRae has left on indefinite leave and was last seen beeing escorted from her office by some
'suits' of the Nancy Reagan persuasion.

I would like to draw your attention here to some very significant facts:-

1. We think faster so when the missiles come in we put up the defense of 'Sorry dear, I did'nt quite catch that !!'
2. My 'WOW' - we are a massive 4% faster.
3. Beware that the other side may button on to the 'thicker' bit and youi use this offensively. (Suggest wiping this from the quotes !!)

Anyways I think my 'other' half is shouting through that there is some good news re the Russian sailors
so I am off to LISTEN attentively. (Apparently)

Cheers.