Derallieur noises

The typical cause is incorrect chain routing.

Your derailleur has a small tab. It's all too easy to route the chain so that it doesn't actually rest on the idler wheels but rather runs on top of a tab.

So, re-check your chain routing. The chain should touch the idler wheels when it goes around them. If the chain runs on top of the small tab, it's incorrectly routed.

Now, how to fix this?

• If you have Shimano chain, you already used the reinforced connecting pin. You need to disconnect the chain at some other location (NEVER at the reinforced pin) and re-connect it using a new reinforced connecting pin. If you don't have a few spare reinforced connecting pins lying around, time to freshen your stocks! It's useful to have few of these pins when you ride around, along with a mini chain tool so you're prepared for chain failures. They're rare but they do happen at the most inconvenient times.
• If you have a chain with a quick link, disconnect the quick link with pliers held diagonally and re-route the chain. Then reconnect the quick link, rotate the cranks so that the quick link is at the top run, press the rear brake and rotate the cranks forcefully forwards. This will re-connect the link. You can usually reuse the quick link (although there are quick links that are a single-use only, so please check your quick link instructions). It's also useful to carry few of these quick links with you.

If ordering new reinforced pins or quick links, please make sure they're correct for your chain. Different gear counts have a different width chain. Each of these widths has a different reinforced pin and a different quick link.

If you indeed put the chain the wrong way, consider just opening the derailleur cage, rerouting it and closing again, instead of unconnecting the chain. At least that's what I did the last time when I had a bad luck with my cheap quicklink pliers.

If you do not have a quicklink, I wouldn't really prefer using the chain tool instead.