If you want to hear radio feeds from real trains, this website let’s you listeen on your computer:
http://www.railroadradio.net/index.php
If you live close enough to pick them up on a scanner, this website lists the radio frequencies that each US railroad uses.
http://www.whrc-wi.org/railfreqs.htm
If you use Real Player you can actually record the feeds. Heck, you could probably store them in Proto 2 systems for playback. Make you own sound files. [:D]
Dep