Depends on your internal setup really
But foam filled suppressors with small exit apertures will definitely reduce your down range noise profile
But it may do next to nothing from where you are shooting the gun.
For example, my VSR sounds like it clacks pretty good when I have my ear right next to the bolt, but from only 15 feet away all you hear is a light click of the trigger and a BB whizzing around
On AEG's, they are primarily for reducing long range noise, like out at 140+ feet, they can be REALLY effective at that. But for CQB purposes, it's really just aesthetic.
Now there are other things you can do to make your AEG really quiet, but that deserves another thread