Using Active Sonar

[Tuee]

On the Kilo mission in the demo, when I use active sonar I can hear the audible returns, but no bright spots show up on the display, even after many pings. I have been able to mark the contacts if I already knew their bearing by clicking on the edge of the "ripple" the moment I heard the ping bounce back... but there must be a better way. Any tips? Could the shallowness of the water in this mission be reducing the effectiveness of the sonar?

[LuftWolf]

The shallow water is reducing the effect of the active sonar.

In terms of the audio only return, this is (reportedly) a common feature of active sonar in real life as well as in the game. The audio amplifier reports the range of the contact but the video amplifier reports the range as well as the bearing, meaning that it gives more information on the contact, and it stands to reason that the video amplifier requires a more high energy return than the audio amplifier, meaning a stronger bounce off of the contact, from it being closer or larger.

In terms of being able to mark the contact when you can't see it, some have asked SCS to change how it works, as currently it is unrealistic and represents a "cheat", although certainly nothing dramatically catastrophic for gameplay.

In other words, the behavior of the sonar array is correctly modelled in the game, as you are experiencing it, except for the process of marking the contact based on audio only returns from the sonar and bearing formation from another sensor, however don't let it turn you off too much, as it is not a "major issue."

I hope that helps. :)

[MaHuJa]

In terms of the audio only return, this is (reportedly) a common feature of active sonar in real life as well as in the game. The audio amplifier reports the range of the contact but the video amplifier reports the range as well as the bearing, meaning that it gives more information on the contact, and it stands to reason that the video amplifier requires a more high energy return than the audio amplifier, meaning a stronger bounce off of the contact, from it being closer or larger.

To me, that doesn't make sense. The audio amplifier ('disconnected' from the visual) would be working omnidirectionally, and would require the stronger signal because it drowns in noise coming from all directions.

If they were 'connected' then the blip strength would determine the audio strength.

The only way I can see that being correct, is if only the audio part filtered so that broadband noise didn't affect it, while the display doesn't filter out frequencies that doesn't have *anything* to do with the ping. And frankly, I cannot believe they were that stupid in making the real thing.


The only last possibility I can think of is that the *real* thing would give you a constant return, as in the sound 'bouncing off' the water itself, which sometimes strengthen when it's hit something more solid like a sub. That could possibly be more sensitive than the display, but would give you audio all the time which the return itself could easily drown in.

... except for the process of marking the contact based on audio only returns from the sonar and bearing formation from another sensor, however don't let it turn you off too much, as it is not a "major issue."

... Problem is, you don't need to know the bearing ahead of time. You can do the 'click cheat' on it - trying every bearing - and only the spot where the target actually is will actually be marked as a contact.

[Molon Labe]

The shallow water is reducing the effect of the active sonar.

In terms of the audio only return, this is (reportedly) a common feature of active sonar in real life as well as in the game. The audio amplifier reports the range of the contact but the video amplifier reports the range as well as the bearing, meaning that it gives more information on the contact, and it stands to reason that the video amplifier requires a more high energy return than the audio amplifier, meaning a stronger bounce off of the contact, from it being closer or larger.

In terms of being able to mark the contact when you can't see it, some have asked SCS to change how it works, as currently it is unrealistic and represents a "cheat", although certainly nothing dramatically catastrophic for gameplay.

In other words, the behavior of the sonar array is correctly modelled in the game, as you are experiencing it, except for the process of marking the contact based on audio only returns from the sonar and bearing formation from another sensor, however don't let it turn you off too much, as it is not a "major issue."

I hope that helps. :)

Are you sure about that? I thought that in DW, the ping is ALWAYS audible as long as the contact is in max display range... That's a bug, not a feature.

[Amizaur]

Yes, there's bug in 1.01. Will be fixed in retail version and patch, the new demo 1.02 has active sonar fixed already. But still the return can be usually heard before something can be seen on the display, it's probably something similar like narrowband lines visible where there is nothing on broadband yet. Common sense says it should be reversed (i.e. blip on the screen visible first) but real world sonar operators says it happens in real world, that you hear the return with nothing on screen... strange but if so then maybe it's realistic...

[LuftWolf]

I don't see how it makes sense for a display method that gives more information on the contact to require a less energetic return. :hmm:

[Tuee]

Yes, you're right—I see it now. An omni-directional microphone will almost certainly pickup more signal than one only looking in one direction, but obviously it won’t have any directional information about it. The argument that the omni-directional microphone “drowns in noise coming from all directions” is incorrect—it will pick up more of everything, including the signal. To put it in statistical terms, because the “sample” is larger, the power of the test is much stronger. The return-ping ought to “jump out” more against the background of all that sampled data.

With all data gathering sensors, there is a tradeoff between sensitivity and acuity. An interesting illustration of this principle would be the human eye. The indirect (or peripheral) vision has greater sensitivity to light and motion, but images in this region will appear more “blurry”; whereas the direct vision has the ability to see in very fine detail, but has less sensitivity to small amounts of light. The reason it works this way is because the photoreceptors in the indirect vision are networked together by special cells called interneurons which cause neighboring photoreceptors to fire when just one fires—so when one goes off it will trigger a whole bunch, and the overall effect is a brighter (albeit blurrier) picture. The fovia (centre of the retina where the image from the direct vision is projected) has very few interneurons compared to the edges of the retina, thus it is less sensitive but has much higher acuity (which we need in order to read or play computer games).

So LuftWolf is right—a weaker return can’t contain more information than a stronger return, and an omni-directional microphone has the best chance of picking up a weak return.

What about passive contacts—in DW do they appear first in narrowband or broadband? (Does it vary from platform to platform?)

[Tuee]

Just to followup, perhaps what would be beneficial (for all I know, this exists in the real world) would be a "range only" indicator for the active sonar that could give the range of the returns even if the signal wasn't strong enough for a directional signal. (Sure would beat watching the ripple.)

One of the few tactical situations where I can see using the active sonar is when I've already fired on a passive subsurface contact and I want to wire-guide them in for the deathblow. In which case, I only need range anyway since I already have a passive bearing.

[LuftWolf]

A fellow diver trained in perceptual science, eh? It's good to know there are more than one of us. :) :up:

In stock DW, contacts will generally show up on NB before BB in virtually all situations.

In the LWAMI Mod, since we have retuned the performance of the sphere array to be more sensitive, quiet contacts will show up on BB intermediate/long term (for US platforms) before the NB, but will show up on the NB before the short term BB. I have information that the sphere array is more sensitive to BB noise than NB contacts, due to the fact that it is suitable only for high frequency NB signals, which don't travel as far as lower frequency NB contacts.

[LuftWolf]

One of the few tactical situations where I can see using the active sonar is when I've already fired on a passive subsurface contact and I want to wire-guide them in for the deathblow. In which case, I only need range anyway since I already have a passive bearing.

You are absolutely spot on in your tactical assessment here.

[Bellman]

:sunny: Some nice stuff here - thanks guys. :|\

I've posted a link to this thread at TnT. :up:

[XabbaRus]

A fellow diver trained in perceptual science, eh? It's good to know there are more than one of us. :) :up:

In stock DW, contacts will generally show up on NB before BB in virtually all situations.

In the LWAMI Mod, since we have retuned the performance of the sphere array to be more sensitive, quiet contacts will show up on BB intermediate/long term (for US platforms) before the NB, but will show up on the NB before the short term BB. I have information that the sphere array is more sensitive to BB noise than NB contacts, due to the fact that it is suitable only for high frequency NB signals, which don't travel as far as lower frequency NB contacts.
Hey Luft you got a link to that info....want to check some stuff out.

[Sonoboy]

I think it's in the readme for the mod.

[LuftWolf]

A fellow diver trained in perceptual science, eh? It's good to know there are more than one of us. :) :up:

In stock DW, contacts will generally show up on NB before BB in virtually all situations.

In the LWAMI Mod, since we have retuned the performance of the sphere array to be more sensitive, quiet contacts will show up on BB intermediate/long term (for US platforms) before the NB, but will show up on the NB before the short term BB. I have information that the sphere array is more sensitive to BB noise than NB contacts, due to the fact that it is suitable only for high frequency NB signals, which don't travel as far as lower frequency NB contacts.
Hey Luft you got a link to that info....want to check some stuff out.

If I were to write a bibliography for the mod, I'd list that under "personal correspondance, anonymous." You're probably not going to find that on the internet, but I seem to remember someone bringing it up on Subsim at some point.

[MaHuJa]

Yes, you're right—I see it now. An omni-directional microphone will almost certainly pickup more signal than one only looking in one direction,

That's exactly where I claim it's wrong.

It will pick up the same amount of signal as a correctly aimed directional receiver, but it will pick up noise from everywhere in addition to what the directional picks up.

but obviously it won’t have any directional information about it. The argument that the omni-directional microphone “drowns in noise coming from all directions” is incorrect—it will pick up more of everything, including the signal.

It's the same amount of SIGNAL acoustical energy arriving at the sensor, while the directional one ignores NOISE acoustical energy from everywhere else.

To put it in statistical terms, because the “sample” is larger, the power of the test is much stronger. The return-ping ought to “jump out” more against the background of all that sampled data.

Remember that what you're looking for, in statistical terms, is an aberration. (I think statistics one uses another word? Doesn't really matter though.)

Which of these stand out?

1 2 4 3 6 1 5 3 15 5 4 2

Then, which one stands out here?

12 11 15 9 15 13 19 12 15

And now the next clue - which one stands out THE MOST?


Following up, that sequence presumed the signal itself was rather strong - it produced a 15 vs an otherwise high at 6. If it's weak, the additional variations introduced by the extra noise will bury it.



So LuftWolf is right—a weaker return can’t contain more information than a stronger return,

Which has nothing to do with the discussion. The return contains the amount of information it does, the issue is how its interpretion (or lack thereof) removes information from it.

and an omni-directional microphone has the best chance of picking up a weak return.

This is the point I disagree with. Why did extending a wlan over 5km require directional antennas, when omni would be better at detecting weak signals? They didn't use one of each on each side either.



Your discussion of the human eye gave me an idea: I think the reason it can sometimes be heard before seen in real life, (that was what they said, wasn't it?) would be an effect of small 'beam width'. Sound doesn't originate from a single point, nor does it move in a straight line. If the sound takes multiple paths that has it arriving from several directions at the same time, and the 'beam width' of the directional receiver isn't big enough to catch them all as in the same direction, while an omni receiver will. That would be the only situation in which an omni receiver should get a stronger signal strength than a directional.

[Tuee]

If the sound takes multiple paths that has it arriving from several directions at the same time, and the 'beam width' of the directional receiver isn't big enough to catch them all as in the same direction, while an omni receiver will. That would be the only situation in which an omni receiver should get a stronger signal strength than a directional.

I think you're making my point for me. As you say, sound travels from A to B along many different paths, thus some signal will approach the sensor directly and some indirectly. A directionally-focused microphone will not register the indirect arrivals, but an omni-directional microphone will--it collects the maximum amount of signal (high sensitivity) making it your best choice for a weak return, but gives you the least amount of information about it (low acuity).

I would imagine that this is also true of passive sonar, however unlike active you MUST have directional information for a passive contact to be of any use (otherwise, you couldn't even sort out one contact from another-- it would just be a bunch of overlapping, convoluted frequencies) which is why there's no omnidirectional TA.

[MaHuJa]

I think you're making my point for me. As you say, sound travels from A to B along many different paths, thus some signal will approach the sensor directly and some indirectly. A directionally-focused microphone will not register the indirect arrivals,
It probably will, but it might not reach a 'threshold' on any of them individually. (meaning it would be possible to synthetically combine them to increase the beam width - probably even after the whole screen range had been done)

but an omni-directional microphone will--it collects the maximum amount of signal (high sensitivity) making it your best choice for a weak return,
It's not "weak" as much as "dispersed". The difference may be rather significant.
but gives you the least amount of information about it (low acuity).

I believe this would be the physics explanation behind it sometimes happening, (as opposed to DW always) quite fixable by increased beam width (perhaps syntethically not to sacrifice accuracy where that is available)

BUT!
-For the 'dispersal' to be enough (it's going to appear on omni *without* appearing on directional though directional will have a better SNR ratio on a 'focused' sound) , there has to be a bit of distance. It would also be quite dependent on the SSP and other acoustical factors. This phenomenon seems to be a function of solely signal strength. (At least that's my observation of 1.01, though they might be in error.)
-Also, such a contact would not be markable. What-so-friggin-ever. Not unless every mark button click would create a contact.
-I'd be surprised if nobody thought of a 'omni amplitude recorder' alongside the returns, perhaps in the middle of the baffle area.
-Why would a synthetic beam width increaser not exist in the real ships and subs?

Oh, and... I still believe there would be a 'constant' omni audio return (environment dependent) that would only spike on a contact, instead of sound only when it 'hit'.


Making the point on directional vs omni sensitivity, I believe the sonobuoys operate correctly - only in cases of very strong contacts on the screen is there an audible ping.

Only the FFG hull active sonar reach isn't much farther, and has this effect in full force. What gives?

[SeaQueen]

One of the few tactical situations where I can see using the active sonar is when I've already fired on a passive subsurface contact and I want to wire-guide them in for the deathblow. In which case, I only need range anyway since I already have a passive bearing.

Active actually isn't so bad to use once you've been spotted by another submarine, it's already shot first, and you need a quick way to find exactly where he is so you can give him something to think about.

Surface ships often get better active sonar ranges than they get passive sonar ranges. Since their counter-detection range is typically longer than their sonar range, acoustic stealth is not something they spend a lot of time worrying about.