noise when engine is cold. ford cougar 24v?

i have an accoustic noise like a very deep toned air horn, that comes from the air intake when the car is cold and idling. it goes when i pull off/drive off. the garage has not offered any answer as it goes when the engine has warmed up. however my mate seems to think it is a fault with my idle control valve sticking. this makes some sense as the revs are unsettled when the engine is cold.
would very much like a second opinion as no one seems to have an answer.
Thanks

PhilyB
March 2011