Some time ago F. Alton Everest came out with a book on critical listening. Along with it came a CD with all sorts of different noise in it from 60Hz hum on up. Meant to aid in trouble shooting I found it was also a great aid in learning what to listen for. Sadly I lost both the book and the CD when I got married and moved.
I think the wife shuddered at the thought of marrying an audiophile reading and listening to such obscure content, so threw them away
Cheers
Orb