Whir from front of engine on cold idle

My 96 has had a whir sound, almost like if you blew in to a 3/4 full beer bottle, when it's idling in the morning after start up. Kind of like a ZJ fan's whir (which I have and have ruled out as the source).
It lasts till the engine is warmed up and is gone till the next morning.
It seems to be coming from around the PS pump/idler/waterpump/intake area of the engine. It's too low pitched to be a vacuum leak so......????

Yo can pick up a mechanic's stethoscope pretty cheap. They are useful and FUN!

One word of advise, put the earpieces in front of your ears until the probe is in position. One time I was setting the earpieces and the probe got whacked by the fan. My left ear has not been the same since.

How cold? The fan clutch locks up on mine when it is really cold, and it makes a fair amount of noise.