Looks or rather sounds like my car has developed the infamous centre airvent rattle

, or at least i think thats where it's coming from.
It sounds more like a buzzing sound, can usually be heard from about 15mph upwards, with the stereo off it can still be heard up to about 60, it seems more noticable when slowing down for traffic lights etc.
If it is the centre air vent should i be able to temporarily stop it by pressing down on the top of the vent?