Both of these sounds are alliterative, meaning they are the same sound in closely connected words. Read the sentence slowly, out loud, to get a sense of the picture that the author is painting here. "ruSHing", "SHrill," and "SteamwhiStle" bring to life the high-pitched sound of the train's whistle, and perhaps the release of steam by the engine. The "r" sounds suggest the power of the train as it moves heavily down the track, creating wind in its wake.
