Broadband vs narrowband sonar

[Dr.Sid]

Main difference compared to DW is the delays induced by finite sound speed will be correctly simulated, to such extent, that it alone will allow active sonar simulation.
Each sound will 'travel' and 'hit' other platforms in correct order, where it will get detected (for passive) or bounced (read new sound event will be generated) for active sonar. This is general mechanism how sound will get from source to listener.

This is actually what I'm working on in the moment.

As for transmission loss, layers, channels and so on, nothing like raytracing is possible because of huge amount of computing it needs, so it will be just lookup tables based on range, depth of listener, depth of target. However I plan to have these changing fluently with daytime and location. I'd also like to have let's say 3 frequency ranges so different frequencies can react differently on sound speed profile.

As for sound source, it's clear DW's 4 constant lines per platform is huge simplification, and I plan to have quite complex sound sources, since it's cheap. So there will be many components, each related to expected cause, and variable not only in amplitude, but in frequency too, where it should be. Propeler noise, flow noise, gear whine, pumps, steam noises, generators, you name it. And of course, correctly simulated transients, which will generaly be samples played (and heard on listener side) when some specific event happens (like torpedo tube opened, or coin dropped :rotfl.
This will make identification much harder and description of sub wont be 4 frequencies. Expect long process of guessing and ruling out. You should be able to tell 'this is ruskie sub' quite soon, while it might be hard to tell if it's delta III or delta IV. Anyway this rich possibilities will easily allow each hull to be slightly different.

As for listener side gear, it will just look slightly more complicated, there is nothing much wrong with it in DW, except it's simplistic at some details.

Of course there will also be MUCH more false contacts, and there will be better environment simulation.