Just a few observations on the above, my experience does not concur here!
I run a Falcon FN 19 at 26ft lb with a Falcon full mod (no detwanger), it is just as loud as my CZ .22lr with subs and a SAK, a pal has an 80ft lb Daystate and Mod and that is noisier than BOTH!
Ammo available for a .22lr runs from about 30ft lb caps, to 205ft lb, so a massive choice, no need to lug a bottle round all the time and recharge after a handful of shots (approx 8 shots per full charge on the Daystate----30 on my Falcon) and the .22lr is likely to be approx 1/4 to 1/2 the price of a FAC Air Rifle.