I do believe the 24/7 pinging refers to the game's method of determining when the escort's ping... If I remember and paraphrase correctly from one of Ducimus' posts a while back (months ago?), it goes something like this:
The escort will ping if your sub is:
- in the "cone"... the area in front of the escort where the escort can ping
- within the active sonar range of the escort
- orientated so that the escort will receive a strong return
Hence the "24/7" term... regardless of whether the escort's crew "realistically" should be actively pinging at that point, or whether the escort suspects your presence, if the above three conditions are met, then the escort is going to ping, and it's going to find you.
The above refers to when the escort isn't "suspicious"... I've had times where the escorts are alerted to my presence, and they're pinging, but they're not in a position or orientation where they're gonna find me. *shrug*
I normally play "Dead is Dead"... which makes the above really tedious. I seem to fare well against destroyers... but I dread subchasers. I've currently got a saved game in front of a large early war convoy, with a subchaser out in front of the convoy. The weather is fair (no large waves), the time is just past sundown, and this subchaser seems to have perfect eyes and ears. If I'm close enough to recognize him as a subchaser, and I've got my 'scope up for any length of time, he seems to zero in on me. If I sit at 1 knot, silent running, at 270', and he gets close enough... he hears me.
If I can keep enough lateral separation, at 270', and orientate my sub so that I keep him off my beam (in other words, my bow or stern is pointed at him, reducing the return of his ping), then I can manage to sneak undetected as he passes me. Pop up in the middle of the convoy, wreak havoc, and get away.
The fun part I'm finding is the convoy scattering as soon as I launch my fish... and somehow, as a result, I'm still managing to miss. It's frustrating, but a good frustrating.
I'm also trying to find a fool proof way of measuring the exact speed of the convoy with the above tactic, since laying submerged to avoid detection means you can't keep popping the 'scope up to take stadiometer readings. I'm thinking I need to keep out in front of the convoy for a bit, matching speed and direction, and verify the convoy's speed that way.
I'd love to see Ducimus' video, too, if someone's got a copy laying around. I'll hit ducimus.net first, though.