static subs still emits noise?

Vipper · 01-05-12, 11:58 PM

I wonder that enemy AI Victor launched couple of torpedoes on me (Improved Kilo) while i was completely standing, engines off, at 130 meters making zero noise. Yet enemy detected and targeted me somehow.

We were very close indeed but still...HOW? And he was moving while targeting. AI cheats?

I reloaded situation again and again and he did find me EVERY TIME.

Hinrich Schwab · 01-06-12, 12:29 AM

I haven't read the doctrine files to confirm it, but the Russian subs have HF Sonar arrays which double as both an "ice thickness sensor" and a passive detector for static objects such as mines and other stationary objects, like a sub. I know the one on a Kilo Improved works up to roughly 3km. If you are real close, chances are the HF array detected you, giving him a solution. The ACTUV Tactics sim, built with the DW engine, also models HF arrays and if the target is in range, it is busted by the array, no questions asked. Being silent won't help. I am certain it is the same in DW. How far away were you from the Victor when this occured?

TLAM Strike · 01-06-12, 12:37 AM

Your generators are still running because your sonar, air conditioning, light etc needs to keep running. Even at all stop a diesel boat makes some noise. If you shut down every piece of electrical equipment you could in theory evade sonar detection but you can't do that in DW.

That is the IRL explnation, but as Schwartzritter said it most likely had you on HF sonar.

magicstix · 01-06-12, 01:51 AM

He heard your crew singing. Next time let them know about proper quiet ship procedures.

I don't think DW models Akulas going HF, it certainly doesn't make sense from a doctrine standpoint.

Hinrich Schwab · 01-06-12, 02:52 AM

The HF is not reliable for much more than finding mines, but the engine does allow for HF detection by platforms with such arrays. I just created a quick mission in in the game to test the theory using an Akula II and the N. Korean Midget Sub. While the blip did not really show in the HF monitor at all, I pointed the boat and the scope in the general area and the engine placed an HF mark in the vicinity of the target, so it is conceivable that if someone is close enough, the HF can mark the player and trigger AI doctrine. I think OP's issue is a very rare case, however.

Molon Labe · 01-07-12, 03:01 PM

At 130 meters, HFS is very likely the source, but I wouldn't rule out a passive detection at base (contact speed = 0) passive level either.

Vipper · 01-07-12, 10:55 PM

Quote:

Originally Posted by magicstix

He heard your crew singing. Next time let them know about proper quiet ship procedures.

I don't think DW models Akulas going HF, it certainly doesn't make sense from a doctrine standpoint.

Maybe he heard how i clicked switches

He was few km away from me, no more and my silent ambush failed...

Oh, are tubes flooding noise modeled in game? I did that.

Dr.Sid · 01-08-12, 10:52 AM

IIRC subs do emit noise when static. There were some graphs with noise vs. speed, and all subs, including Kilo, did emit some noise at speed zero. The noise was very small. The noise also did not increase until 5kts or so. Simply speaking static sub makes same noise as slow sub.
No transients like opening tubes are generated by AI subs, nor detected by any sub, AFAIK.

IMHO at 130m you simply detected you. Depends on the background noise. I literally crashed into Kilo once without detecting him, but it was stormy sea.
At 130m he could actually create a shadow on BB by masking background noise. Not that it is simulated in DW.

magicstix · 01-14-12, 02:21 PM

Quote:

Originally Posted by Vipper

Maybe he heard how i clicked switches

He was few km away from me, no more and my silent ambush failed...

Oh, are tubes flooding noise modeled in game? I did that.

I'd say tubes flooding would definitely be a detectable transient; I dunno if DW models that though.

magicstix · 01-14-12, 02:22 PM

Quote:

Originally Posted by Dr.Sid

At 130m he could actually create a shadow on BB by masking background noise.

Your source on this?

Dr.Sid · 01-14-12, 05:20 PM

Quote:

Originally Posted by magicstix

I'd say tubes flooding would definitely be a detectable transient; I dunno if DW models that though.

It does not. At least if AI is involved on either side. Not sure about player vs. player, as many things are different with player boats.

Quote:

Originally Posted by magicstix

Your source on this?

Just a rumors I'm afraid. But imho it's plausible. Questions is at what range such effect would occur.

magicstix · 01-14-12, 05:50 PM

Quote:

Originally Posted by Dr.Sid

Just a rumors I'm afraid. But imho it's plausible. Questions is at what range such effect would occur.

I wouldn't expect it to occur due to diffraction except at collision ranges.

Dr.Sid · 01-14-12, 06:43 PM

130m basically is collisions range.

magicstix · 01-14-12, 06:50 PM

Quote:

Originally Posted by Dr.Sid

130m basically is collisions range.

Maybe for foreign boats.

Still I wouldn't expect 130m to be close enough to cause shadowing of a sonar array.

Dr.Sid · 01-14-12, 07:35 PM

I did some simulations .. just in 2D, and just with masking object of shape of circle (ie approximation of sphere in 3D) .. and it seems that even waves twice the size of the masking object leave some shadow. At wavelengths at same size the shadow is rather well defined and protrudes many wavelengths behind the masking object.

Sound comes from left, as planar waves. I've tried point source too, but it looks about the same. Te wavelength is 8 pixels, so is diameter of the masking object. The brightness is average amplitude over time. Ie you don't see individual waves, without any interference the picture would look like flat are with brightness slowly dropping with distance.
In these kind of simulation, sound reflects of any part which does not 'move' .. ie. also from borders of the simulation. To prevent it, border 50 pixels are 'attenuation zones' .. amplitude there is artificially attenuated so the sound is absorbed, rather then reflected. Even so some of the sound can be seen being reflected from top, bottom, or even right border. The circles in front of the blocking object are interferences of incoming and reflected waves, and they nicely show wavelength of the sound.

If we take Kilo as 10m diameter, and if we look for frequency with such wavelength, it would be about 150Hz. IMHO we can take the picture as rather good simulation of sound at 150Hz bending around Kilo sub.
150Hz is rather present in usual background noise. Higher frequencies would be masked even better, but background noise drops quickly with frequency.

I know sub guys usually go ultra silent when someone talks about 'how does Kilo look on sonar' .. especially when someone mentions 'hole in the water' .. but my bet is at 130m and silent, Kilo would be spotted as shadow on BB. Or anything at that size.

Sure my simulation is pretty crude, and I don't have anything 'official' to compare it with .. it might be totally off .. but it's my 2 cents ..

01-05-12, 11:58 PM	#1
Vipper Machinist's Mate Join Date: Sep 2007 Posts: 122 Downloads: 8 Uploads: 0	static subs still emits noise? I wonder that enemy AI Victor launched couple of torpedoes on me (Improved Kilo) while i was completely standing, engines off, at 130 meters making zero noise. Yet enemy detected and targeted me somehow. We were very close indeed but still...HOW? And he was moving while targeting. AI cheats? I reloaded situation again and again and he did find me EVERY TIME.

01-06-12, 12:37 AM	#3
TLAM Strike Navy Seal Join Date: Apr 2002 Location: Rochester, New York Posts: 8,633 Downloads: 29 Uploads: 6	Your generators are still running because your sonar, air conditioning, light etc needs to keep running. Even at all stop a diesel boat makes some noise. If you shut down every piece of electrical equipment you could in theory evade sonar detection but you can't do that in DW. That is the IRL explnation, but as Schwartzritter said it most likely had you on HF sonar. __________________

01-07-12, 03:01 PM	#6
Molon Labe Silent Hunter Join Date: Jun 2004 Location: Along the Watchtower Posts: 3,810 Downloads: 27 Uploads: 5	At 130 meters, HFS is very likely the source, but I wouldn't rule out a passive detection at base (contact speed = 0) passive level either. __________________

01-08-12, 10:52 AM	#8
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	IIRC subs do emit noise when static. There were some graphs with noise vs. speed, and all subs, including Kilo, did emit some noise at speed zero. The noise was very small. The noise also did not increase until 5kts or so. Simply speaking static sub makes same noise as slow sub. No transients like opening tubes are generated by AI subs, nor detected by any sub, AFAIK. IMHO at 130m you simply detected you. Depends on the background noise. I literally crashed into Kilo once without detecting him, but it was stormy sea. At 130m he could actually create a shadow on BB by masking background noise. Not that it is simulated in DW. __________________ ComSubSim forum at CADC

01-14-12, 06:43 PM	#13
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	130m basically is collisions range. __________________ ComSubSim forum at CADC

01-06-12, 12:29 AM	#2
Hinrich Schwab Grey Wolf Join Date: Nov 2010 Posts: 908 Downloads: 89 Uploads: 0	I haven't read the doctrine files to confirm it, but the Russian subs have HF Sonar arrays which double as both an "ice thickness sensor" and a passive detector for static objects such as mines and other stationary objects, like a sub. I know the one on a Kilo Improved works up to roughly 3km. If you are real close, chances are the HF array detected you, giving him a solution. The ACTUV Tactics sim, built with the DW engine, also models HF arrays and if the target is in range, it is busted by the array, no questions asked. Being silent won't help. I am certain it is the same in DW. How far away were you from the Victor when this occured?

01-06-12, 01:51 AM	#4
magicstix Captain Join Date: Aug 2011 Location: Nuclear submarine under the North Pole Posts: 481 Downloads: 1 Uploads: 0	He heard your crew singing. Next time let them know about proper quiet ship procedures. I don't think DW models Akulas going HF, it certainly doesn't make sense from a doctrine standpoint.

01-06-12, 02:52 AM	#5
Hinrich Schwab Grey Wolf Join Date: Nov 2010 Posts: 908 Downloads: 89 Uploads: 0	The HF is not reliable for much more than finding mines, but the engine does allow for HF detection by platforms with such arrays. I just created a quick mission in in the game to test the theory using an Akula II and the N. Korean Midget Sub. While the blip did not really show in the HF monitor at all, I pointed the boat and the scope in the general area and the engine placed an HF mark in the vicinity of the target, so it is conceivable that if someone is close enough, the HF can mark the player and trigger AI doctrine. I think OP's issue is a very rare case, however.

01-14-12, 07:35 PM	#15
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	I did some simulations .. just in 2D, and just with masking object of shape of circle (ie approximation of sphere in 3D) .. and it seems that even waves twice the size of the masking object leave some shadow. At wavelengths at same size the shadow is rather well defined and protrudes many wavelengths behind the masking object. Sound comes from left, as planar waves. I've tried point source too, but it looks about the same. Te wavelength is 8 pixels, so is diameter of the masking object. The brightness is average amplitude over time. Ie you don't see individual waves, without any interference the picture would look like flat are with brightness slowly dropping with distance. In these kind of simulation, sound reflects of any part which does not 'move' .. ie. also from borders of the simulation. To prevent it, border 50 pixels are 'attenuation zones' .. amplitude there is artificially attenuated so the sound is absorbed, rather then reflected. Even so some of the sound can be seen being reflected from top, bottom, or even right border. The circles in front of the blocking object are interferences of incoming and reflected waves, and they nicely show wavelength of the sound. If we take Kilo as 10m diameter, and if we look for frequency with such wavelength, it would be about 150Hz. IMHO we can take the picture as rather good simulation of sound at 150Hz bending around Kilo sub. 150Hz is rather present in usual background noise. Higher frequencies would be masked even better, but background noise drops quickly with frequency. I know sub guys usually go ultra silent when someone talks about 'how does Kilo look on sonar' .. especially when someone mentions 'hole in the water' .. but my bet is at 130m and silent, Kilo would be spotted as shadow on BB. Or anything at that size. Sure my simulation is pretty crude, and I don't have anything 'official' to compare it with .. it might be totally off .. but it's my 2 cents .. __________________ ComSubSim forum at CADC