how to be undetectable?

[allanon87]

hi friends,
i started the campaign of DW from russian side. In the first mission i have to controll the "traffic" avoiding to be detected but some sub are close to me (2-3 nm) so some questions arised:
-how much can i go fast?
-can i use the streaming wire for radio message?
-how is important the depth for passive sonar?
-if i prepare the torpedos for firing someone can hear that?
Can you help me?

[Blacklight]

-how much can i go fast?
-can i use the streaming wire for radio message?
-how is important the depth for passive sonar?
-if i prepare the torpedos for firing someone can hear that?
Can you help me?

-how much can i go fast?
In general, with enemy ships around or anywhere within a few miles away, I usually don't go over 4 knots. Maybe 5 if you're in a hurry. But do it sporadically. Also, if the enemy is pinging, a good strategy is to point your sub toward or away from the pinger. The less surface area of your sub that the sound waves from his ping can hit, the better.

-can i use the streaming wire for radio message?

Yes. No one's going to see it.

-how is important the depth for passive sonar?

It depends on the depth of the sea floor and the sound propogation. It's more a matter of stay slow and low. I usually try to skim along to bottom but you have to be real careful when doing this or else the enemy will suddenly hear a loud "crash" if the sea floor suddenly changes depth and you don't watch where you're going.

If you're talking about your passive sonar, that also depends on depth and wether or not there's a thermal layer present. If you're above the thermal layer, you can't hear anything below it and vice versa so it's a great place to hide and use tactically. Not every environment is going to bless you with one of these though. I believe the first campaign mission is in pretty shallow water so it definitely does not have a thermal layer.

-if i prepare the torpedos for firing someone can hear that?

I don't know if that game models that at all. I know in real life, they can hear it. It's something I've done before entering very hot zones. Maybe someone with more knowlege than I have can answer this one.

[CapitanPiluso]

Here you can find some more (real world) info

http://www.maritime.org/fleetsub/sonar/index.htm

[allanon87]

first of all thanks guys for answer, very useful. thanks for the document it's great!!Back to thread.

you're right i'm in shallow water so there isn't a thermal layer, so i will stay deep, but now i know that i can go faster than 1-2 knots. In fact for fear to be detected that was my operation speed.
thanks for the document it's great!!.
About passive sonar: when i stay near the floor of the sea enemies can hear me with more difficult...that's mean even me can hear him more difficult?

[Pisces]

Originally Posted by allanon87

...

About passive sonar: when i stay near the floor of the sea enemies can hear me with more difficult...that's mean even me can hear him more difficult?

Won't work. You make the same amount of noise near the bottom as above. Until you make a nose dive, then you are louder.

Active sonar directed at you might theoretically give you an edge because the echo of the bottom and your echo almost coincide. But don't count on it. Your sub is still a very good reflector compared to the seabottom. And in-game I don't think this is modeled at all.

[allanon87]

i assumed that the different speed of the sound between sea floor and surface helped me to be more undetectable....so i was wrong.
but i'm quite sure that near surface (20m depth for expample) an enemy radar can find me, that's right?

[Pisces]

Originally Posted by allanon87

i assumed that the different speed of the sound between sea floor and surface helped me to be more undetectable....so i was wrong.

Oh ok, you mean curved soundwaves because of soundspeed changes with depth. In reality the sound is curved towards depths with lower soundspeeds. So it is either bend back to the surface, or into the depths if there is a maximum. And both bottom and surface might cause it to reflect. If there is a minimum speed somewhere, then the sound is bobbing up and down around that depth. This is called the deep sound channel. How the sound curves from or towards you is complicated, especially how much of it arrives at the listener. Dr.Sid made a simulation program to illustrate this by ray-tracing. It's called SoPro iirc. There should be a thread about it somewhere over here.

The game simplifies this sound physics allot. On the other side of a layer you are pretty much undetectable. Unless you get within a certain distance from a surface contact, then it is a direct path detection. This distance is dependent on your depth. DrSid did found this out in a series of tests on detection ranges some years ago. Again, do a search.

but i'm quite sure that near surface (20m depth for expample) an enemy radar can find me, that's right?

Radar doesn't penetrate water. But sometimes you do if you are too close to the surface, and the waves are bad.