you can hear plenty if you stick a rag in each exhaust pipe end for a few seconds while you have a listen (sounds like a washing machine full of scrap iron IMHO)
I had a loose flywheel last year on the 996 .Rode up the M1 cruising at 90 for 100 miles and I recone it was loose a long time before that. The noise was not that distinguishable as it was progressive but when the bike was checked on a service sure enough the fly was loose. I would say its vibrated more and the noise came from "within",with the noisy clutch most of these "noises"are hidden and difficult to pin down.4D
probally not what you have but.. I had a bloody funny knocking noise comming from what sounded like the front of the bike..found out that the last person to put new wheels and tyres on the bike didnt do the rear nut up enough and the clip was the only thing holding it on..... me not best pleased ...