A short video of the sound differences between Moto3 (250cc), Moto2 (600cc), and MotoGP (1000cc). The camera ended up clipping a little audio because they are so loud, but there is enough to show the general idea. This was from the IndyGP 2012 at turns seven and eight.
I like the sound of the Moto2 bikes when they are in a pack.
