Thanks for the site, moemusic.
I'd read about the process of taking samples of "silent" parts of the source for use as a noise profile. I've even used it a few times on some of the material I have. It is a tricksy thing to get right.

I did not know about the possibility of a time/temp variation!
More complexity. Whoo! More reading too.
Should keep me warm and busy this winter on these cold Buffalo nights.

And I thought it was hard learning to build Tube Amps!