The benchmark for quiet pcp airguns has been and still is the Benjamin Marauder. That is what you should compare the various offerings to. Granted, there are now other guns which are even quieter than the Marauder, so when comparing, see how the company ranks the Marauder.
To give a bit of perspective, the pellet hitting a squirrel at 20 yards will make more noise to you as the shooter than the Marauder's muzzle report. A pellet striking a wood fence is substantially louder yet.