DW sound propagation model measurements

Dr.Sid · 07-22-07, 06:07 PM

Uh .. so exact filling of area between rays showed little more complicated than it seemed son I only solved some basic cases and SoPro 1.1 is not ready for release yet. But it looks promising !

Dr.Sid · 07-24-07, 05:24 PM

Another night behind me and I'm getting close to new release. There are some glitches where beams flips (those bright dots and jaggies) and the bugs when editing SSP are not taken care of yet, but whole brand new beam based simulation (rather then ray based) is done. I've also fixed some bugs in intensity, now I'm few orders closer to simple spherical spreading if I try to simulate it.

All random numbers are gone, all non-covered pixels are gone.

Small delta time now only improves bending simulation, not coverage.

Delta angle can be no much higher (I use 5 degrees now !). There are two mechanisms which allows it. First I have beams with non-zero width now, and beam is divided into more if it gets too wide. Like this I can use small count of beams where it is not important and more beams where it is needed. All this can of course be controled by user.

Also interference simulation got better because of better coverage.

Here is quick peek of actual results .. note that delta angle is 5 degrees and delta time is 0.01s !

Other things I'd like to make yet (tomorrow I hope):
- fix known bugs (thanks to all for reports)
- Session save/load (options,ssp)
- individual rays overlay - you will be able to specify another delta angle (let's say 10 degrees) and individual rays will be displayed at this angles, with full intensity (and different colors), so you can see what the sound is doing.
- Intensity overlay - you will be able to display intensity for given depth as graph where intensity will be on Y axis (logarithmic scale)

Possible changes:
- logarithmic display of brightness (not during the simulation, but after it).
- better spline function for SSP definition to allow linear gradients and better control.

Pisces · 07-25-07, 06:32 AM

Congratulations on the progress DrSid. Really looks promissing indeed. *Applause*

But in all honesty, we sort of hijacked your topic. It's not about your DW test anymore (which is interesting enough itself), but about the propagation tool. We best dig up that first Soundpropagation tool topic and continue there.

Dr.Sid · 08-18-07, 10:56 AM

I updated the first post with new convergence zones measurements. Nothing unexpected was found, but the data now are more complete. I've updated both image and text.

In short I can say that CZ are about the same as surface duct. Except:

1) layer is more shallow, shadow zone starts closer.
2) there are the convergence zones, exactly at 30 and 60 nm. That one on 30 nm makes signal stronger from 18 to 39 SNR. That on 60 nm cannot bring the signal above 0 SNR, but on NB display it can change practically invisible line into 2 quite strong lines.

Convergence zones both are pretty narrow, you can cross them in seconds (depending on speed difference) so they are easy to miss.

Pisces · 08-20-07, 06:04 PM

Excellent work DrSid!!

There's one thing I was wondering about the shadowzone(s) from your previous graph and this one. Is that front-edge within 5.5-11Nm below the layer a parabolic shape? The previous graph had more datapoints IIRC. I can understand if it is impossible to say with these results. But it would be nice to know how far you can get into that shadow zone corner.

Dr.Sid · 08-21-07, 04:25 AM

Quote:

Originally Posted by Pisces

Excellent work DrSid!!

There's one thing I was wondering about the shadowzone(s) from your previous graph and this one. Is that front-edge within 5.5-11Nm below the layer a parabolic shape? The previous graph had more datapoints IIRC. I can understand if it is impossible to say with these results. But it would be nice to know how far you can get into that shadow zone corner.

Will do more tests. Both edges have 3 points, but it is not so obvious for the the new one, and both show slight parabolic shape. It's quite steep anyway. For getting as close as possible to moving target you would need some safe margin (you also don't know the distance exactly), so I guess the curve is not so important.
How the start of the shadow zone depends on the layer depth would be more interesting knowledge, but again it will change in tenth of mile.

Dr.Sid · 11-11-07, 08:11 PM

I did some last test of submerged-submerged situations. I have finally cleared all my doubts and I updated (for the last time I hope) the first post once again.

It showed that in the end in DW the sound transmission is symmetric. It means when A hears B, B will hear A at exactly same quality. So if surface listener hears sub bellow the layer with some transmission loss, the sub will hear the surface boat with same loss. If sub bellow the layer is in the shadow zone, surface boat will not be able to hear it and also the sub will not be able to hear the surface boat. Surface won't be able to ping the sub: sub won't hear the pings, and there will be no returns from the sub. This all is correct and realistic.

Please note that this can seem to be broken sometimes, since for example FFG uses long towed array. So it can seem to the array that sub is lost, but for FFG it is not in shadow zone yet and it still can ping it. That's what fooled me few times.

So what we already now, but inverted: sub above the layer can be heard normally. Sub bellow the layer can be heard somewhat worse (30 SNR to 20 SNR, 3 lines to 1 line). Active sonar is affected in similar way. The 'dot' is smaller and you can hear the return. Sub in the shadow zone can't be heard nor pinged.

Now what we didn't know. When the listener is under the layer too, it can hear the sub-layer target even in the shadow zone and the detection range is limited only by distance and gradual signal weakening. That was to be expected. But what is little surprise, the signal too will be weaker then if both target and listener were above the layer. Simply bellow the layer there are worse conditions.

Check the first post for final conclusions.

MarkShot · 11-11-07, 08:53 PM

Okay, I went back to your first post. So, what are your conclusions for the non-expert players; casual players like me?

(1) Except for the shadow zone, thermals do not play a significant role in combat. Fast deductions to accelerate ID and solutions and/or evasive maneuvers to frustrate a solution are more important than the small factors of thermal loss/enhancement on acoustic behavior.

(2) Thermal affects in DW are symmetric unlike in real life.

(3) Acoustics affects are from array to hull. So, it is possible for a hull to be in a shadow zone while its towed array is not. Thus, potentially yielding an asymetric situation with regards to detection.

(4) Both passive and active sonar follow the same model.

Are the above correct?

---

Also, I think one other piece of information you should add in your other notes:

The wash out created by explosion is purely a graphic affect provided to the player to enhance atomosphere. It is not actually part of the acoustic modeling at all.

I have seen this in a number of ways:

(1) Dynamic objects created as the result of a destruction of another object are able to gain contact immediately after an explosion; not at all impeded.

(2) I have assigned trackers immediately following explosions by assigning at known bearings despite whatever is displayed on the screen.

(3) TMA station shows tracking lines being generated during periods of explosions.

What this means for the player is that immediately following an explosion (for the next few minutes), you are a very vulnerable to the AI. (although I haven't tried NB to say if it is degraded during this time ...) This is especially true when close dynamic units are instantiated.

---

Thanks for your detailed work to improve understanding of the game engine!

---

Reference:

http://www.subsim.com/radioroom/showthread.php?t=122769

11-11-07, 08:53 PM	#8
MarkShot Ace of the Deep Join Date: Jul 2002 Posts: 1,134 Downloads: 93 Uploads: 0	Okay, I went back to your first post. So, what are your conclusions for the non-expert players; casual players like me? (1) Except for the shadow zone, thermals do not play a significant role in combat. Fast deductions to accelerate ID and solutions and/or evasive maneuvers to frustrate a solution are more important than the small factors of thermal loss/enhancement on acoustic behavior. (2) Thermal affects in DW are symmetric unlike in real life. (3) Acoustics affects are from array to hull. So, it is possible for a hull to be in a shadow zone while its towed array is not. Thus, potentially yielding an asymetric situation with regards to detection. (4) Both passive and active sonar follow the same model. Are the above correct? --- Also, I think one other piece of information you should add in your other notes: The wash out created by explosion is purely a graphic affect provided to the player to enhance atomosphere. It is not actually part of the acoustic modeling at all. I have seen this in a number of ways: (1) Dynamic objects created as the result of a destruction of another object are able to gain contact immediately after an explosion; not at all impeded. (2) I have assigned trackers immediately following explosions by assigning at known bearings despite whatever is displayed on the screen. (3) TMA station shows tracking lines being generated during periods of explosions. What this means for the player is that immediately following an explosion (for the next few minutes), you are a very vulnerable to the AI. (although I haven't tried NB to say if it is degraded during this time ...) This is especially true when close dynamic units are instantiated. --- Thanks for your detailed work to improve understanding of the game engine! --- Reference: http://www.subsim.com/radioroom/showthread.php?t=122769 __________________ War games, not wars! --- Only a small few profit from war (that should not stand)!

07-22-07, 06:07 PM	#1
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	Uh .. so exact filling of area between rays showed little more complicated than it seemed son I only solved some basic cases and SoPro 1.1 is not ready for release yet. But it looks promising !

07-24-07, 05:24 PM	#2
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	Another night behind me and I'm getting close to new release. There are some glitches where beams flips (those bright dots and jaggies) and the bugs when editing SSP are not taken care of yet, but whole brand new beam based simulation (rather then ray based) is done. I've also fixed some bugs in intensity, now I'm few orders closer to simple spherical spreading if I try to simulate it. All random numbers are gone, all non-covered pixels are gone. Small delta time now only improves bending simulation, not coverage. Delta angle can be no much higher (I use 5 degrees now !). There are two mechanisms which allows it. First I have beams with non-zero width now, and beam is divided into more if it gets too wide. Like this I can use small count of beams where it is not important and more beams where it is needed. All this can of course be controled by user. Also interference simulation got better because of better coverage. Here is quick peek of actual results .. note that delta angle is 5 degrees and delta time is 0.01s ! Other things I'd like to make yet (tomorrow I hope): - fix known bugs (thanks to all for reports) - Session save/load (options,ssp) - individual rays overlay - you will be able to specify another delta angle (let's say 10 degrees) and individual rays will be displayed at this angles, with full intensity (and different colors), so you can see what the sound is doing. - Intensity overlay - you will be able to display intensity for given depth as graph where intensity will be on Y axis (logarithmic scale) Possible changes: - logarithmic display of brightness (not during the simulation, but after it). - better spline function for SSP definition to allow linear gradients and better control.

07-25-07, 06:32 AM	#3
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	Congratulations on the progress DrSid. Really looks promissing indeed. Applause But in all honesty, we sort of hijacked your topic. It's not about your DW test anymore (which is interesting enough itself), but about the propagation tool. We best dig up that first Soundpropagation tool topic and continue there.

08-18-07, 10:56 AM	#4
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	I updated the first post with new convergence zones measurements. Nothing unexpected was found, but the data now are more complete. I've updated both image and text. In short I can say that CZ are about the same as surface duct. Except: 1) layer is more shallow, shadow zone starts closer. 2) there are the convergence zones, exactly at 30 and 60 nm. That one on 30 nm makes signal stronger from 18 to 39 SNR. That on 60 nm cannot bring the signal above 0 SNR, but on NB display it can change practically invisible line into 2 quite strong lines. Convergence zones both are pretty narrow, you can cross them in seconds (depending on speed difference) so they are easy to miss.

08-20-07, 06:04 PM	#5
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	Excellent work DrSid!! There's one thing I was wondering about the shadowzone(s) from your previous graph and this one. Is that front-edge within 5.5-11Nm below the layer a parabolic shape? The previous graph had more datapoints IIRC. I can understand if it is impossible to say with these results. But it would be nice to know how far you can get into that shadow zone corner.

11-11-07, 08:11 PM	#7
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	I did some last test of submerged-submerged situations. I have finally cleared all my doubts and I updated (for the last time I hope) the first post once again. It showed that in the end in DW the sound transmission is symmetric. It means when A hears B, B will hear A at exactly same quality. So if surface listener hears sub bellow the layer with some transmission loss, the sub will hear the surface boat with same loss. If sub bellow the layer is in the shadow zone, surface boat will not be able to hear it and also the sub will not be able to hear the surface boat. Surface won't be able to ping the sub: sub won't hear the pings, and there will be no returns from the sub. This all is correct and realistic. Please note that this can seem to be broken sometimes, since for example FFG uses long towed array. So it can seem to the array that sub is lost, but for FFG it is not in shadow zone yet and it still can ping it. That's what fooled me few times. So what we already now, but inverted: sub above the layer can be heard normally. Sub bellow the layer can be heard somewhat worse (30 SNR to 20 SNR, 3 lines to 1 line). Active sonar is affected in similar way. The 'dot' is smaller and you can hear the return. Sub in the shadow zone can't be heard nor pinged. Now what we didn't know. When the listener is under the layer too, it can hear the sub-layer target even in the shadow zone and the detection range is limited only by distance and gradual signal weakening. That was to be expected. But what is little surprise, the signal too will be weaker then if both target and listener were above the layer. Simply bellow the layer there are worse conditions. Check the first post for final conclusions.