I had the 16", and I didnt really think it was as quiet as some folks claim.  It is certainly 'quieter' than lets say...30-30 or something, but the shorter barrels are of course louder.  I get quieter loads with my longer SKS loaded sub-sonic with big bullets.  I have looked into these loads quite a bit for pests in my chicken coop.  The best thing I have found is a long barreled .22 rf loaded with 22 CB ammo.  The normal CB's work great in my tube mag, and they have CB long that will work in a  clip magazine.  These are fun bullets to shoot, and definatel have enough poop for close work.  I used to have a Marlin 22 bolt rifle, and that was the quietest of all.  A single shot with a 21-22 inch barrel would be awesome.