Can't help on the legality issues in your local, but have shot enough pellets to have an idea about sound levels.
Pellet guns aren't silent, and the "magnum" ones have a fairly loud report. That said, pellet guns don't sound like a firearm and hence you're unlikely to have a neighbor think you are firing a gun due to the sound. Now if they see you with a pellet rifle and they are of the easily offended sort, I have no doubt they'd call the cops on you.
