The mercury lamp if fused gives that kind of a noise. you should replace the lamp with a new one and most likely it will be sorted out!

Buzzing sound is most likely coming from the fused lamp. to cross check just remove the lamp and replace the lamp cover and try switching on the projector, if the sound disappears , just replace the lamp! if the sound persists the Ballast power supply that powers the lamp could be faulty!

If the filters new and the Fans are running at the normal speed , then its most likely ur ma inboard that needs replacement! We have had a few of these units come with the mainboard problem! Cheers

Its your DMD that needs replacement! Replace it and ur projector will be good as new!

apart from the fans , u also need to double check the qulaity of the lamp that you replaced lately [ if you have ] if yes , then thats the answer to ur problem! try and get a genuine lamp, will save ur projector's optical engine in the longer run! Cheers