When this loco travels, it sounds like it's also playing the sounds a buggy would make rolling across whatever terrain is under the tracks, is this a side effect of the way the animated wheels are done?

Hmm, probably...
Honestly, the wheels were done by the original author and I just try to maintain it, so I don't exactly know why it is

I played around with the file but could not find the issue and it was talking to long (copy to the zip dosen't work well for whatever reason, aka i had enough as i waste to much time). What i want to ask, is it possible to send a message to the devs and ask them to have a look? Because the train look so beautifull and also is compatible with the elevated rails (for anyone who want to see what i mean, use https://mods.factorio.com/mod/yi_railway/discussion/688c04dae0fecb13c03777b6 to add more trains. When you try to go up/down, the sprites will still be horizontal since no "elevated rails" sprite exist")

Also thank you for maintaning it. If i where to sugest a change, remove the sound entierly until a fix has been found since yeah, that noise is to much, so no sound it's still better then not using this mod because of that train.