Weird noise from engine bay

[arctic_97]

I've noticed a weird noise coming out of my engine bay. It's not a squeal or a rattle but almost like a vacuum being purged. It repeats every few seconds (this occurs with all accessories off, didn't try with them on). It appears to be coming from the frontal area, near the fan maybe. Anyone got any ideas?

Car is a 1997 M3 coupe, has about 65K miles and I do have the water pump scheduled to be replaced soon.

[BMoW]

This happens with my car when its cold outside and my car is cold also like 40's and below. Its like a vibration and when I start to move my engine almost sounds diesel-esque. WIERD. But after my engine has warmed up everything goes away except for a very slight sound that only I and a friend of mine can hear. It happens when I get on the gas. But its so quiet that it best can be heard within 500 rpm's above my idle (600 rpm). It sounds like a ccchhhhhhhhhhhhhhhhhhhhh sound like if someone kind of is hauking a luggy. My service manager told me it was my belts which that is where the sound seems to be coming from.
Mo