Open the file trainzoptions.txt, which you will find in the folder where Trainz was installed.
Add the line -disablerailjointsound
Be sure to include the - as the first character, and leave no spaces
Save the file onto itself (replacing the original copy). On some systems, you may get a permissions error when you attempt to save in the TS folder. I had to change permissions so that my user had all permissions.
This will eliminate all built-in track sounds, including junction and the silly click-clack sounds.
You can get content that will have its own sounds, which sound much more realistic. The sounds for this content will still work with the change described above.
Hope this helps
CP