Chain noise on changing gear

[summerdays]

I notice this noise when I'm changing gear, specifically its when I change up to the large chain ring (I think its when I change up, I've forgotten now I'm off the bike), I sort of get a noise but not every time. Now I spent some time on a cycle path changing up and down to see if I could work out what is happening. The only thing I noticed was that on the occasions I got the noise the dérailleur had pulled forward, slowish and then slaps backwards generating the noise. Then it appears to be under normal tension. Other times when I don't get the noise it doesn't move as far forward.

Now is this an adjustment needed (to what) or a new dérailleur? (or part of).

It doesn't happen when changing between the small and middle rings.

 

[Globalti]

It's normal for the chain to rattle briefly against the sides of the cage when changing gear. If it continues after changing, the cable needs tightening or the limit screws need adjusting.