[CapnScurvy]

First off......Welcome to SubSim JimPierce!!

You say you've been using the "convoy training mission" and the sound goes away after a time compression increase. Are you trying to hear sound while the compression is on? If so, it probably doesn't work. Some functions of the game stop working with ANY time compression setting (if you happen to be in the outside camera view when you add time compression, your conning tower team will vanish).

I'm assuming you're talking about this sound problem occurs when you return to normal time. I haven't used the training missions in quite a while, but it's my impression they aren't worth a tinkers damn! I don't know under what files the training missions are modeled, but I've always had a feeling that what occurs during a training mission is different than what will occur during a Campaign played game. It's like they used different files to make the training missions than what's played in the rest of the game. My suggestion is to scrap the training missions (they get you familiar with the control use and that's about it), just start a Campaign at the date you wish, and go from there.

The game has bugs-a-plenty, I'm more inclined to think your sound issue is related to the training mission files than anything else. I doubt that the training missions were intended to use time compression anyway. Their short and sweet and are only going to provide limited functionality, my advice......move on into the game.

It's true if a ship cruses at a speed below half its "Maximum" rated speed, you'll not hear its sound when you take the Hydrophone....even though your sound man can. I've not looked at all stock ships.....I'm hoping the Dev's realized this would occur and they kept the ships scripted routing speed above half its Maximum during all missions......but, this issue comes into play when a modder doesn't realize this short coming, and has a ships Maximum speed lowered causing the unmodified ship's speed during a mission to be below the half Max value. This won't allow for the ship to be heard. This can, and will occur with some mods. Because its related to each individual ship parameter, one ship may be heard, while another that's traveling at the same speed will not.