I've used a Surefire supressor on my MSAR, and it cuts down on the sound, putting it more in the .22 range.
Not as quite to me as on an AR, but 1. the action is closer to your ear 2. Any piston gun is going to be louder supressed than a DI gun - more gas escapes into the environment without going through the supressor is most likely the reason, as I would think the small ID gas tube on a DI gun has less volume of gas going through it than the volume going into a piston tube.
Still worth putting on. Now on my MSAR anyway, there is a point of impact difference between with/without the supressor. The AUG may have a tighter barrel lock up and so this could not be an issue - only one way to find out.
Even if so, the platform is so short you can run a can on it and still have a short weapon, so just sight in with the can on and rock and roll.