The original “Hush Puppy” was a Smith & Wesson Model 39 pistol fitted with a suppressor for use by Special Forced in Vietnam. The name came back in the 1980s, when the US Air Force requested a suppressor for use with the M9 Beretta in its pilots’ survival kits. Knight’s Armament developed a design that used a clever and very quick snap-on attachment method. It was a wipe-based suppressor, with a functional lifespan of about 25 rounds. The pistols were fitted with slide lock levers to further reduce the sound of firing. Approximately 3,800 were supplied to the Air Force, and a few years ago, the company sold about 188 of them on the civilian market.
In practice, this combination is indeed extremely quiet. The report of the shot definitely became louder over the course of about 20 rounds fired, though.