Try using CB caps. Very quiet! Good for shooting squirrels or pests when you don't want to disturb anybody.
I experimented with all brands of CB caps, but the accuracy is not there, and they are only good to about 35 yards. At 50 yards, I found a lot of vertical stringing of groups with CB caps. I can get one-hole groups with sub-sonic LR ammo at that distance. With the 26-inch barrel on my Anschutz, the .22 LR sub-sonics are as quiet as the CB caps are in shorter barrels, with way more power and way flatter trajectory. I don't need anything quieter. There is no muzzle blast noise using sub-sonics with that barrel. If using super-sonic ammo, you get the "crack" noise of the bullet breaking the sound barrier. With sub-sonics that is gone. In shorter-barreled 22's, I don't notice much difference in noise between sub-sonic 22 LR ammo and high-velocity ammo. The long barrel is the key.
I wish more companies would make long-barreled 22 rimfires for the noise reduction alone. Very few people know about this noise reduction because very few people have shot sub-sonic ammo in a 26-inch barreled 22 rimfire.