You might like to checkout my 'BAD sound FX post' which relates to similar sound issues. I've had a supposedly higher performance card installed,
which hasn't made a jot of difference in helping to eliminate the noise issues that I experience in TS12 & TANE. One suggestion I received was the make of card
was at fault,i.e. a Sound Blaster, rather than a Realtek ???. However other than the obvious question, and which you have mentioned, 'why are only those two
Trainz games affected, and not others'. I would also be interested to know if other TS users, other than yourself have had sound issues when running sessions, etc.
Although the problem is slighter less audible in TANE, amongst the questions I now need to ask myself, is do I pump more
coin into another sound card in the hope that that particular make, or model, will work the oracle, and if indeed the problem is even related to the sound card!?.