Hi Philipp
I think the ' hiss maker' file you are looking for is :-
data/Sound/Collision_AntiSubmarineNet_int.wav
This is called when harbour defences are being drawn before a patrol starts.
Originally, in Stock SH3, it was more like an ear splitting screech. Your fellow Brazilian, Rubini (
) , saved the hearing of many headphone wearing Subsimmers by turning down the volume in his Harbour Traffic mod so that it was inaudible. Other mods followed suit.
It is present in all the mods I've just looked at (NYGM, GWX, WAC)....its just that you can't hear it in-game. Although you can if you simply play the file from the Sounds directory
Cheers
Cheapskate