suppressed air guns ???

Yep. Lots of the higher power ones are made that way. The hammer is louder
on my 900FPS NP (with lead / over 1200FPS with alloy) than the noise out of
the barrel, and the sound of a pellet hitting a gopher is louder than that.
My neighbors don't even know when I am target practicing with it unless they
see me.

Even some of the bigger bore PCPs are suppressed.

Most call it a shroud, but if it's a chamber with vents from the muzzle it
suppresses. Some are better than others. Lots of Xisico owners modify one
off an RWS because it works better.