[XenonSurf]

What do you mean by a 'sound file which triggers when your boat is detected'? Sounds like a cheat to me, you should never know when you are detected (although you can probably set the OFEV in order to know...).

What is not a cheat is that your radio operator (or the enemy one) if he is competent, he can intercept messages from other ships, and one of these messages can be a detection report of your boat, although I don't think that in real-life 1940 this was done so easily... It is also only of little tactical benefit because you should almost always assume you are detected if you get too active or too close, and expect some planes to come join the party. That's why I always move away at flank for some time after finishing dealing with enemies, so I confuse any possible radio report which was sent. Real skippers surely did the same.

It's a fatality that the commander of the Bismark was underestimating enemy radio interception capability. This was the main reason for his destruction instead of reaching safely the port of Lorient I think. It's curious that submarine tactics were more aware of this, a reason why most subs were equiped with the 'Enigma' coder for messages.