Today's diesel locomotives do not have whistles. They are equipped with air horns.
A reproduction of a Southern Pacific Railroad 6 chime steam whistle.
A typical modern 5 chime air horn
As many folks have stated on here, yes it is possible to hear train horns from many miles away depending on weather conditions and the terrain features between you and the railroad.
Boy, that Ellwood Haynam really had that whistle sound down!
It was a modern train sound, and now I am educated as to the difference! Love that modern chime sound, which isn’t all THAT modern, because I think I’ve been hearing it since I was a kid in the 50s, right?