Tip on hiding from DD's sonar (Real Life)

[MaxT.dk]

Differences in seawater temperature help subs hide out. By lurking right below the thermocline (PASSING THERMAL LAYER...), the layer between the surface and deeper waters, subs can avoid some sonar pings from ships or aircraft trying to detect them. That's because sound waves distort when passing through varying water temperatures.



Hmm, I wonder if this trick works in SH4... :hmm: :know:

[General Tso]

Yes it works very well.

[General Tso]

Oops, I just noticed the icons after your last sentence. I guess you were'nt asking a question.

[nomad_delta]

For the 'thermal layer' effect to help, does one have to hide right below it (that is, stop diving immediately after passing thermal layer) or just anywhere below it, including much deeper?

Also does being below the thermal layer help with hiding from just passive sonar/hydrophones -- or does it help hide from active sonar (pinging) too?

nomad_delta

[John Channing]

Anywhere below it and it helps with both.

But it is not a "cloaking device". You still have to be slow and stealthy.

JCC

[V.C. Sniper]

The deeper the better

[DirtyHarry3033]

Like JCC said, anywhere below the layer helps but you can still be detected by sonar.

The layer is an "interface" between warm water (close to the surface) and cold water (well below the surface).

Picture yourself in a fishing boat on a crystal-clear lake, you look down thru the surface of the lake and spot a fish just below the surface. You take a frog gig and attempt to spear the fish, aiming directly at what you see. Well, you will miss!!!

Why? Well the "interface" between the air and the water refracts the light rays, they are "bent" so that the target you are looking at is not where it appears to be from your point of view. You can still see it, but it is not where your senses tell you it "is".

If your fish was lying on the beach, above the surface of the water, it would be no problem to spear him, right?

The thermocline does the same thing, except with sound waves. When you get below the layer, the enemy still knows you're there but it's much harder for him to pinpoint your location since his active sonar is refracting off the layer. Or, if he's listening passively, your sound emissions are also refracting off the layer.

In either case, the sonar return received by the DD will appear to be coming from someplace that it's not. And as V.C. Sniper said, the deeper below the layer you are, the more the return gets refracted. Once the DD's find me, I'll generally dive to 400+ feet, go silent and creep at 1-2 kts. They're dropping DC's in my general area because they have a rough idea where I am but it's rare for one to hit close enough to damage me...

However, make too much noise and you'll eventually be pinpointed ;) The layer is not an invisibility shield!

DH

[Go4It]

Playing with Kakemanns Improved Escorts mod, was hounded by 4 elite DD after sinking 2 ocean liners, couldn't lose them for 2 hours, even at the deepest depth I dared go they still found me. I said %$%$#@#@ this an ordered all stop, with in 15 minutes all DD were gone. I tried this other times an it works. Done know if it's Kakemanns Improved Escorts mod or a bug in SH4

[nomad_delta]

Here's a question, brought about by my recently getting pummeled and nearly blown to bits by DD's after an attempted convoy attack:

I'd heard that it's a good idea to go to Flank speed when you hear depth charges exploding, 'cause the DD's can't hear you over all the noise. Actually I'd heard it's a good idea to go to flank as soon as you hear the splashes, but my sonar man never tells me when he hears splashes (or much of anything else for that matter, the useless bastard... have to do everything myself) but I've never really been able to hear the splashes myself, just the explosions. I thought I heard splashes a couple of times, but they weren't always followed up by actual explosions so maybe I was imagining things, and I definitely wouldn't want to go to flank speed when they weren't actually depth charging me 'cause that'd give me away real quick.

I'd also heard that even after the depth charges have stopped exploding, the destroyers still can't hear you even if you're moving a flank for some time afterward because of the noise from all the bubbles from the explosions.

So I guess a few questions, really:

1. Are the 'splash' noises of depth charges hitting the water definitely modeled in the game, and can you guys hear 'em?

2. Is it it really a good idea to go to flank speed while they're dropping depth charges?

3. Is the thing about the bubble noise true, and if so, how long can one safely continue moving at flank speed after the last depth charge has exploded?

nomad_delta

[DirtyHarry3033]

Nomad those are good questions. Not having the source code, I can't say what's modelled in the game but IRL if there are DC's detonating, the DD won't hear sh*t! The detonations will be much louder than any sound from your sub even at flank speed.

Regarding "splashes" nope I've never heard 'em and never gotten a report of DC's in the water from sonar. That's disappointing. So I "cheat" and if I have a close DD contact on sonar I go to external cam, if he's really close I watch him drop the DC's, wait a reasonable time then go to flank and knuckle port or starboard and order a change of depth to throw off his aim on the next run. When the explosions die down, I go back to 1/3rd.

OK so that's "cheating" but my sonarman should tell me when he hears a splash, right? A DC will make an unmistakable sound when it hits the water, he should hear it, right? But he don't, so I cheat...

DH

[heartc]

I'd also heard that even after the depth charges have stopped exploding, the destroyers still can't hear you even if you're moving a flank for some time afterward because of the noise from all the bubbles from the explosions.

So I guess a few questions, really:

1. Are the 'splash' noises of depth charges hitting the water definitely modeled in the game, and can you guys hear 'em?

2. Is it it really a good idea to go to flank speed while they're dropping depth charges?

3. Is the thing about the bubble noise true, and if so, how long can one safely continue moving at flank speed after the last depth charge has exploded?

Yes, those are very good questions and I was wondering about the same as far as the time they are still deaf after the explosions is concerned. Well, the DD who's just dropped on you will definetely *not* hear you for a short time after that, cause he's at that point usually still at flank speed from his depth charge run and you are in his baffles. Question is if the explosions and aftermath have also drained out your noise for other DDs in the vicinity. I honestly don't know. I just keep flank speed up for some 4-5 seconds after the explosions and hope for the best, otherwise it would be pointless accelerating at all.

What I *do* know is that the game has the sea state background noises having a pretty big influence on hydrophone effectiveness. The AI, at least the stock AI, has a *very* tough time detecting you the more rough the sea state is, and you yourself will also notice increased background noise when manning the hydrophone (this last one might be my imagination, but the AI definitely is far worse in rough seas). So there might really be a chance that those charges are recognized as causing a locally limited, temporary increase of sea state which makes hydros become less effective. But this is only speculation on my part. Would be great to hear something about it from the devs, or modders who might know it. (As a sidenote: The nuke subsim "Dangerous Waters" has gotten the sonar model down pretty well. At least that's what people say who did this kind of stuff for a living. In this sim, among other things, when you struck a target for example and it explodes, you can't hear anything except the loudest surface contacts for several *minutes*. Don't even dream about raising a submerged sub during this time.)


About the sound of DCs splashing into the water: Yes, you can hear them when you are manning the hydrophone yourself and have it trained in the approximate direction of the tin can. It's a bit subtle and doesn't really sound like you might expect a splash to sound though - it sounds like "Woohoppp, Woohoppp". If no one is in the room with you right now, then move your mouth like a fish does while audibly sucking in air at the same time - this comes closest to what it sounds like. ;)

What I'm doing when under DD attack is I usually man the hydrophone myself. At the same time, I still have the hydrophone man reporting on the nearest contact, which will usually be a DD, while I'm trying to track the rest and keep my wits up. The sonarman by himself is really ineffective, like he was in SHIII, and can only track one target at a time. For an effective defense, you really have to man the station, cause you need to know the bearing change rates, engine speeds etc for several DDs, at least those who are close to you. The only feasable alternative to that is using the "map contact updates on" option. I would use it myself if it didn't also give away all ship positions when surfaced. Of course, you could make it a rule for yourself to simply not look at the map screen when at PD or surfaced, but then you can't plot anything either if you want to.
Using the outside view on the other hand makes it way too easy though imho and gives you abilities even a modern nuke submariner could only dream about. ;)

[the_belgian]

Tip on hiding from DD's sonar (Real Life) :hmm: :know:

Stay out of the water :rotfl: :rotfl: :rotfl:

[CaptBC]

Once below a thermal layer go silent (if you haven't already);) and order the engine room to make rotations for 1 or 2 (no more than 2) knots. I use 1 knot and slowly slink away from those pesky destroyers!:up:

CaptBC

[nomad_delta]

I'm running Trigger Maru 1.2 and I think Ducimus made the DD's a lot smarter/more aggressive/difficult to evade. Even when I drop to 1-2 knots and max out my depth and try to slink away they always seem to find me and depth charge me repeatedly anyway.

I've discovered that even though my sonar man is nearly entirely deaf and doesn't tell me anything useful at all, if I listen through the hydrophones myself I can in fact hear the 'splashes' of the depth charges hitting the water. (Actually a couple times I took a peek through the observation periscope and actually saw the depth charges dropping next to me.

So I've taken to going to flank speed immediately as soon as I hear the splashes (if I'm lucky enough to be manning the hydrophones and pointing them in the right direction at the right time, that is) and keeping it on for about 6-7 seconds, then dropping to 1/3 or all stop to drift along.

The DD's are relentless though, and keep going straight over me with active sonar and dropping more depth charges, so I just keep repeating the same process and making 45 degree turns now and then... with any luck after 15-20 depth charge attempts they give up and go back to their convoy. Or more likely they get lucky and blow me to bits.

It's nerve-wracking, lemme tell ya. ;)

nomad_delta

[MaxT.dk]

Hide under one of the merchants, or just just behind it, works here and DDs can't depthcharge you because the merchant is in the way :know:

[starvingartist507]

according to the numbers in the data files:

if below the thermal layer, the hydrophone signal is reduced to 33% and the active sonar signal is reduced to 20%. so dropping below the thermal layer reduces your sub profile by around 70% on both active and passive sonar.

Seems to me that once I get below thermal, in most cases I can just go silent and sneak away on a constant heading. I guess this is why. That doesnt seem wrong, and it makes shalow seas even more dangerous.

I've discovered that even though my sonar man is nearly entirely deaf and doesn't tell me anything useful at all, if I listen through the hydrophones myself I can in fact hear the 'splashes' of the depth charges hitting the water. (Actually a couple times I took a peek through the observation periscope and actually saw the depth charges dropping next to me.

There is a whole other thread about the sonar man and his failures. To summarize: he is suppsed to warn you of a depth charge attack, of a DD successfully pinging you, and of a DD on a direct attack run.

[SteamWake]

subs can avoid some sonar pings from ships or aircraft :o

Hrm...:hmm:

Sorry just having some fun.

[SteamWake]

There is a whole other thread about the sonar man and his failures. To summarize: he is suppsed to warn you of a depth charge attack, of a DD successfully pinging you, and of a DD on a direct attack run.

Dont forget no warning of those pesky circular runners.