When sensor of SH3 was discused, i remember some USA NAVY information, about WW2 subs, at silent runing was very stealth, an hydrophone must be between 50m to detect it... of course if you was pinged by active sonar... bad luck. But the hydrophone has lot of job to detect a sub in silent runing condition.
The info was from USA NAVY.
I think so we must to be well protected at silent running.
I made a mod to obtain a good silent running protection for SH3... it works fine, if you dont do any stupid thing, you remain well protected. So you can maneuver to be not exposed to the active pings...