You know what the problem is? All the sounds in Railworks are all very close together in volume - loud.
The the sounds currently are is like this: a horn being a value of 1.00 in the .proxyxml file (we will image 1 is 100% max volume possible), and there is a bird chirping at a volume of 1.00 in the .proxyxml file, then the bird would theoretically be as loud as a train horn in real life. Now wouldn't that be a terrible world to live in?
What should be done, is all other sounds be turned down, with horns being the loudest sound in the game, represented as 1.00 in the .proxyxml, then say, the engine at idle being a mere 0.15 in the .proxyxml file, and the engine getting louder to around 0.5-0.65 at run 8 in the file. So the engine is realistically quieter than the horn, which, when you turn up your volume to max to make the engine sound at realistic volume out of your speakers (as I have been doing in my experimental soundpacks), the engine sounds realistically loud, and the horn is realistically deafening.
I may post a video of it soon if I can get my sounds properly working again (I changed something recently that made distant sounds really quiet). This creates a MUCH more dynamic audio experience, because the sound from the game has, what is called in the music industry, a much better Dynamic Range. Imagine a modern pop song where everything is really loud. That's the current sounds. Now imagine an older vinyl, any genre, choose your poison. The sound is much more dynamic, being that you can hear quieter instruments in the background, but loud vocals, or a powerful guitar solo.
That is what making quieter sounds quieter in the files does. I don't like using compressors on sounds, because it flattens out the volume of the sound, making parts of the sound which are supposed to be quiet unnaturally loud, rendering the sound much, much more fake sounding, as well as driving the gain up until it clips, as, well, it clips, and no one likes the sound of popping where it shouldn't be.

But enough of this, I've said too much for this post to be in this section. Should be in the 'Sound Application' section after this post.

They exist everywhere. You may not see them, but they're there. Awww yeeeaaaahhhh, 20% Cooler! /)