22 LR makes about 130 db and looking at this chart there is a vast difference in the 22 vs air gun noise.
http://www.straightshooters.com/documents/decibelrating.htmlWhen air guns exceed the sound barrier, 1100 fps or so, there is a loud crack and also the pellet will destabilize, making it less accurate.
I have a 177 pump pistol and a 22 co2 carbine and both are much quieter than my 22 pistol. Both air guns shoot at less than 750fps and are only effective to about 70 yards.
