You know I've ben whining about passive detection range until I read this

[Castout]

The link is here http://www.computerharpoon.com/wiki/...le=Sonar_model

Let me quote a little, it's been stikied in the DW mod section. I thought this was worth sharing.

After reading this well it seems that DW is a better game than SC. . .in terms of passive detection range.

And an unspeakable mod actually made some of the stuffs told in the article a reality such as the impossibility of detecting diesel boats.

So I say wow thank you Sonalysts.

Sonar in Real Life

Passive Sonar
Sea state and Target Noise always causes the biggest changes to sonar predictions. Target Noise and Target Speed were always calculated as one entry = Target Self Noise. Likewise, Receiver Self Noise, Receiver Speed, and Cavitation were grouped together as = Own Ship Noise. They were combined because the separate items are directly proportional to each other.
With newer nuclear submarines at speeds below 10-12 knots you're talking about detection ranges of less than a mile. Diesel submarines can become undetectable passively because they can shut down everything that makes noise, regardless of how modern they are. A modern diesel at a 2-3 knot patrol speed is probably not detectable beyond 1000 yards passively, less in high ambient noise environments. Obviously, a lot depends on ambient noise, propagation paths, layer depth, the sensitivity and location of the passive sonar receiver, proficiency of the submarine crew and operating mode, etc. In fact, in an inshore environment (shallow water, high ambient noise, high shipping density, high wreck density), attempting to track a diesel submarine passively is virtually impossible, and extremely difficult actively, and the US Navy relies primarily on non-acoustic methods for initial detection, i.e. a periscope search using ISAR radar being the most effective. MAD in a shallow water environment is handicapped also... wrecks, bottom topography, geologic features, etc., all contribute to false MAD contacts and high magnetic noise, reducing the detection range. For that reason, passive detection range for a diesel submarine in shallow water should be Zero.
Factors limiting active sonar performance in shallow water (the littoral environment) also play a major role... active sonar frequency and power affect bottom reverberation and absorption. Bottom compositions are rated on their ability to absorb and reflect sound energy. A muddy bottom will absorb a lot of energy, whereas a rocky, gravel bottom will reflect and scatter a lot of energy. Again, wrecks will give false contacts. A good diesel sub CO can avoid active detection by going dead in the water and pointing the bow or stern towards the sonar, reducing the target strength by as much as 80 per cent and not providing any Doppler return to the sonar. Or he can bottom, in which case his target echo is masked by the bottom reverb, and if he bottoms near a wreck you've got more problems.
The big point is that the environment pays a major role in the ranges observed. A Victor III in the Norwegian Sea (relatively quiet sea and deep) at 12 knots may be detected at several miles. The same submarine in the Med (relatively shallow and very noisy) may be detected at a 1000 yards. At flank speed (27 knots), the Victor III may be detected at 20 miles direct path, 25-40 miles bottom bounce, and possibly to 3 or more CZ's (convergence zones) at 30-33 miles, 60-66 miles and 90-99 miles in the Norwegian Sea, by ship based sensors and sonobouys, and for literally thousands of miles by SOSUS. What you see here is an overlap of ranges depending on transmission path, and that is entirely normal and expected. SOSUS exploits the deep sound channel, low frequency noise propagated for thousands of miles in a duct created by the effects of pressure and temperature at those depths.
This is just the tip of the iceberg, and my intent was to point out that you can't just assign hard and fast numbers. Under the right conditions a carrier may be detected acoustically well in excess of 140 miles, or may not be identified at all until it's in visual range. Assuming the carrier is detected at 140 miles, can the operator classify it as a carrier? Maybe, maybe not. If he is operating a sophisticated narrowband acoustic processor, possibly, assuming the carrier isn't using acoustic deception. If it is a broadband system (namely an active sonar being used in a passive mode), all he knows is something is making a lot of noise on a given bearing. That, combined with other intelligence may provide another piece of the puzzle, but you can't definitively classify a target with broadband sonar. A carrier launching and recovering aircraft is a different story. The noise of the catapults hitting the water brakes every 30 seconds or so is very distinctive, can be heard for long distances, and any submarine acoustic analyst has probably been trained to recognize that sound. A more comprehensive list of variables:

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read from the link if you're interested