My house is in the middle of a terrace of Police houses (so cops living on both sides) and backs onto a Police pursuit center. I' ve never had so much as a raised eyebrow pointed at me when I rip paintballs into the brick targets in front of old pallets at the end of my garden. I have set them up so that the paint only splashed onto my compost head and won't go over the fence.
Just the other day we were just leaving my patio doors a open a couple of inches, sitting well inside the living room and firing at the end of the garden. If you stand outside you can't hear the marker fire at all, just the "fffwwwwwwip" sound of the balls going past. Love that sound!