Chainrings being not perfectly round causes chain tension to be high (or correct) in most of the revolution and loose in the rest. When the chain tension loosens (at high revolutions) the chain will oscillate, causing some of the noise. Put your bike in the stand and pedal at about 60 rpm and watch to see the chain vibrating. It's like if you stretched out a rubber band and plucked it. If so, get a new chainring (or just deal with it).
This is, of course, after you clean the **** out of your chain and lube it back up.