No, it doesn't look like it. The way the sound propagates in the duct doesn't look quite right either. There's definitely some things not happening with that one, but you're on the right track.

I remember someone saying that. It's almost like DW needs "The Complete Geeks Guide to Dangerous Waters."

Maybe it's just because the bending is so increased to be visible on such small range.

Otherwise this is exactly what you said .. interference between reflected and non-reflected waves. It's true that this is just snapshot in time, not optimistic nor pessimistic case.

But interference can only happen with concrete frequency. Each frequency will form different interference pattern, and noise will not interfere at all. That's what I mean by saying it will affect active sonar more, because it uses concrete frequency, while passive also detects noise.

I'm looking for the book.

That might be the case. I'd have to see it done without that to be sure, though. You just used Snell's Law, right? How did you change it to exaggerate the refraction?

It definitely looks like an interference pattern. I just wasn't quite sure if it was the Lloyd mirror pattern.

I think you're thinking about the difference between passive and active sonar incorrectly. Because of various affects, an active sonar has to listen over a wide band pass as well. If you didn't, you couldn't exploit Doppler. Both active and passive sonars are also influenced by noise. You can limit the influence of noise in both by using various filters. Passive sonar can detect broadband signals, or narrow band signals, depending on the filtering. Broadband tends to increase your noise level but narrow band decreases it by selecting out specific frequencies. Depending on what you're doing, you might listen for broadband signals, or you might listen for discrete narrow band tonals, in which case the energy is "binned" by frequency (which reduces noise) and averaged over time to further reduce noise in that frequency bin.

If you want to play with a basic sound propagation simulator:

http://www.jhu.edu/~virtlab/ray/ray.html

It's Snell law alone. Interference is simulated by computing instant intensity based on distance from sound source - sin(distance*2*pi/wavelength). That gives both positive and negative amplitudes. On places where positive and negative meets because of surface reflection you can see signal strength decreased. As I said, it's just moment in time. I guess the effect should be integrated thru time for at least 1/f. Will try tonight, together with correct scale.

I hope understand all these effect, I just don't know which is important IRL and which not and to what amount. I have the book ordered anyway, cost me $60, so I hope it will be good. :rock:

btw. I hope this general sonar info is not bothering anyone here. DW is the only game concerning sonar to such depth (well, together with it's predecessors)

Simple but nice. I just don't understand the difference between sound speed and velocity. :nope:

I think the velocity speed is for the 'wind' speed

http://www.jhu.edu/virtlab/propagation-of-sound/

I see ! Thanx ! Must try it in my tracer to see how big effects this can have.

the wind speed versus the sound speed should not have a lot of effects in my opinion.

SeaQueen: In those old pictures you can see individual waves of sound energy, one specific moment in time. But waves move.

Here is a new picture which sums the effect in time and thus gives average energy transfered to that point. The time window is very short, only half of the wave-time, but it is enough to remove patterns of waves itself.
Now the patterns looks quite different. These pattern does not depend too much on bending multiplications, I guess beacuse they are formed mostly by reflection from the surface. So I let the bending still multiplied (30 times to be exact).

PS: book seems to be on its way

http://roger.questions.cz/other/integrated.jpg

Hello there lady and gentleman.

Why don't you check out the forum of this project ?
It's located here:

http://games.groups.yahoo.com/group/communitysubsim

We started working on it. We didn't give this up (yet :rotfl:).
There is even first piece of code released (simple 3d view of Foxtrot sub).

We have just 6 members now. Common .. don't tell me you are not interested at all ! At least watch us as we fail ! :|\\

Failure is not an option :) the 3d viewer looks good and I hope we can get more help too.

Yes sir ! I just wanted to make it more interesting :rotfl:

Digging up an old thread, sorry.:oops:


I am wondering, will our sim support GMAX models? I've got the program, nothing to do with it, and am wondering if Xabba could use a "second hand" in his work?


I'm already working on a quick 688i model, and how would I send it to you if I needed to?

What's GMAX ? :|\\

I now use 3ds format. I can use any well described format. I could use pretty any format and reverse engineer it, but since there si so many good described formats and most modelers can do exports to them, I hope there will be no need.

I especially have good experience with Wavefront OBJ and Lightwave LWO.

But now the fastest way is to provide 3DS.

Also there is forum dedicated to the sim and it's kinda dead now, so please post any questions there:

http://games.groups.yahoo.com/group/communitysubsim

Its a freeware 3d modelling tool.

Yeah .. I won't ask stupid questions without googling it first :rotfl:
Looks good.

Yeah, I joined the group, I just posted here since it looked pretty unused.

Excellent thread, ladies and gentlemen!!!

I was wondering how long it would take the community to rise up and create their own cold war subsim. I almost started my own similar development, years ago in the sub command times, after being desillusioned from it but then switched to a WWI project finally.

I am also a big hydroacoustics nut, trying to design my own fancy hydroacoustics and sonar model but have other priorities now.

I am also much into ship dynamics on which I focus for quite a while now.

Anyway thumbs up to Dr.Sid for the couragous attempt to pull out a cold war subsim and all the best. :up:

Do not run out of steam, the community will not forgive you this.

Deamon