Chain really noisy near front derailleur on low gears but doesn't appear to be rubbing.
Ascertain that the chain is not visibly touching the front derailleur.

Check that your rear cassette is fitted correctly; lock-ring is tight and the correct spacers used between sprockets.

Are you using a matching chain, chain rings and rear derailleur? i.e. are they  all 'n' speed; i.e. do not mix and match a 9 speed chain with a 11 speed cassette or derailleur. 

Is your rear derailleur vertically aligned correctly, not subject to crash damage.

Assuming you're on Shimano, is the b adjustment screw of your rear shimano derailleur correct such that the rear derailleur does not touch the cassette?

Is you rear derailleur compatible with the large sprockets you have on your cassette?  e.g. a short arm rear derailleur may only support up to 25 tooth sprockets.

Do you have the correct length of chain to support the gear range you have.