Hushing sound from engine

I've noticed when taking my fabia 1.2 '06 reg up to the torque band that there's a kind of hushing/chain sounding noise from the engine. I say hushing because thats the only way I can think to describe it and sounds as if the chain belt (told by dealer that 1.2's have chain timing belt instead of rubber) is shaking when I rev it.

Any ideas? I would provide a better description but thats the only way I can describe it!