I'll admit I've never heard any of my guys ever make a noise, but have heard of other people swearing that their beardies do make noises regularly...what you have to be aware of is what Tracie has already mentioned, which is whether or not the sounds are coming from their chest, or rather could it be some form of a cough, wheezing, clicking or crackling, etc. and whether it happens when he is breathing. If it resembles any of those noises or seems to be related to his breathing, it may very well be the early sign of an upper respiratory infection. Those noises from beardies are very common and almost always indicate an URI developing. Also look for excess mucous in his mouth or liquid coming from his nostrils, this is often seen as thick strings of mucous when they open their mouths. If you think it may be at all related to any of these signs or symptoms then he needs to see an experienced reptile vet for cultures and treatment.
Otherwise it's probably just a noise he makes, you may just be one of the lucky ones that has a vocal beardie. I'd be suspicious of illness if this is a brand new thing that he has never done before, depending on how old he is, but if it's possible for you to take a video on your phone or digital camera of him making this noise, then uploading to YouTube and posting a link to the video, we can then listen to it and give our opinions of it...