Full SPeed On X6 then a noise

I've went full speed and full throttle and somehow i hear like this humming sound. It goes loud, then soft, then loud then soft, do you guys know how to fix this problem?

Your engine is about to blow!!!!!!!..............LOL nah just jokin'.......sounds like either the chain or the plastic vibrating...very common....just check the chain for slop, shouldn't have much more than 1/2" and then check all the bolts, especially the rear sprocket bolts.........