Railworks America

That's the "wagons sound pack" from the file library here (look under Miscellaneous) by Krellnut. Yes, it is excellent stuff.

I created a thread on Walter's excellent freight car sounds a while back, to call attention to his great mod:

http://www.railworksamerica.com/forum/viewtopic.php?f=6&t=1574

Its amazing how long we put up with basically no freight car sounds as the train went by.
Thanks again Krellnut. I feel its one of the top 5 best add-ons for RW, and its created by a user,
not RailWorks.