It's not the blower motor chirp... Already had that fixed.
The best way I can describe it, is to say that it sounds like an air hose with moisture in it, spitting sound. It comes and goes at random. It is still present with all accessories off (radio, HVAC, lights), and stops when the truck is turned off.
With it being so cold, I haven't had a chance to crawl under there and get a visual... just thought someone might know what it might be, and could save me a few minutes.