Airguns on the whole are fairly quiet when compared to shotguns and centerfire rifles.
But any lessening of the ‘crack’ that comes from your barrel will ultimately help you whilst out hunting. For target work or back garden plinking it’s not necessary but if you want to improve your hunting success, a moderator will help.
There are plenty of moderators to choose from. Some are just a chamber where the air behind the pellet is allowed to expand before exiting the muzzle, thus reducing the crack. More effective ones use a series of baffles, which can be purpose-shaped metal, and plastic.
Whatever type and size of silencer you use make sure its a perfect fit over the muzzle and is in perfect alignment with the bore of the barrel. If the muzzle of your airgun is not already threaded, a screw on silencer is best fitted by a gunsmith, but simpler sleeve-fit designs can just slide on to the barrel and be fixed in place by tightening a grub screw. Its always best to fit a silencer before you go to the trouble of zeroing your rifle because the moderator can have a very slight effect on velocity and also trajectory of your pellet, which can push your zero out.
Silencers are also called moderators. This is because the cylindrical device that many airgunners fit to their rifle barrels moderates the sound, rather than totally silencing it. Its true to say that some moderators do a better job than others.
For example, pre charged airguns can be more effectively moderated than spring- powered airguns. That’s because most of the power developed by the action on a PCP is a small tink of the valve opening and closing. The noisy part comes when the compressed air leaves the barrel, but its relatively easy to damp this down.
A spring gun has all the commotion of the spring expanding and crashing into the end wall of the compression chamber. You can lessen this noise if you take your springer to a skilled gunsmith who will polish and tweak the internals to make them smoother; or buy a springer with synthetic bearings like the Air Arms Pro-Sport.