This game really needs some Ambiance. I'm not sure if its in it or not, but it sounds dead. It needs something like birds at day, and crickets at night.
I know this has been brought up in the past and it is certainly something that all the routes are lacking. I'm sure it is something that is being worked on and hopefully life will be brought to TSW!
Ambient noise is a lot louder than your average train sim will ever give respect to. The world is just so quiet without a train around...
Can't see it happening until that audio update for UE4 comes out. I don't think people would be happy that they couldn't hear the engine of their loco because the audio channels were being used by chirping birds. Good idea for later down the line though.