AC Interior Noise: Varies with Speed

[cebra]

I have read through threads on blend doors, actuators etc but I couldn't find what my truck is doing. I have a fairly loud interior noise from PS foot well area when I turn my AC on. It varies with rpm (not speed). It is a kind of rattling, brrrt, noise like a wheel bearing when it starts going out but definitely coming from inside or around the hvac box under the dash. What part would this be, doesn't sound like a blend door from what I have read? I may need to check to make sure the AC blows cold on the PS side though to be sure.