Iirc, and I have seen them in person, slings are not “quiet”. They make a whoosh whoosh whoosh sound that can be heard from 50 yards away as the slinger winds up.
I was talking about the slingshot, not the classic sling - but of course that makes a noise, too! I like watching slingers and have seen a lot of videos - one guy only did the “windup” twice and it was almost soundless, until his shot hit the target.
Thank you for correcting this, however! Have a good one.