Weird sound at idle...

[OCD90]

I have this intermittent sound at idle...it's sort of like a muffled horn blowing, and if I give it a bit of gas, it goes away...and it's never there under load (like a power breaking scenario). It's very similar to the sound I hear every time I turn the car off. I know this isn't much to go on, but does that ring a bell?

I don't think it's a belt noise...maybe a pully? Bearing? Hard to say...but suggestions are welcome.

[Mike Hippert]

Pop the hood and look around. check all your fluids one may be low.