Without being able to inspect it, I'd have no definitive way of knowing. However, I will say that with my experience, a lower humming would suggest a fan, while a hum with a higher pitch would suggest the color wheel is at fault. Again, to know for sure, it's probably best to have it inspected.
My DLP started having a humming sound coming from it about a week to 10 days ago. There has been no change in the picture quality, color, or anything of the sorts. I first noticed it due to a short burst of a loud winding and then it would stop. It happened about once or twice a day. Now it has a constant low humming.
1. Is this the color wheel or another fan?
2. Does the color wheel need to be replaced or can you just clean it?
Any help would be appreciated.