What is the most quiet pistol with a silencer?

Answer 1

single shot or semi-auto with with a slide lock, projectile below the speed of sound, quality suppressor are the most important. Brand and caliber really don't matter if the previous three are adheared to.

Edited to add: I think caliber plays a factor, too. A smaller bore means a smaller hole that sound escapes from. My .22LR silencer sounds a lot quieter with its small bullet moving 1,050 f.p.s. than some 147-grain 9mm ammo I fired though a 9mm silencer, and the 9mm bullets were moving slightly slower, maybe 950 feet per second.

I've noticed that even without a silencer, a .17 magnum rimfire sounds quieter than a .22 magnum rimfire. All I can conclude is the size of the bore matters.