I have heard 22lr firearms with good silencers, they are not virtually silent. I was very impressed with how much the noise was reduced, but they certainly should not appear to be virtually silent to anyone without advanced hearing loss.
As I said there is many types of silencers, but the .22lr can be virtualy silent because of the properties I mentioned earlier. Most production silencers are designed to be practical, working well for a relatively high volume of rounds while being of a practical size. And retaining longevity in the US (because they are NFA items and consumers want thier expensive taxed and registered product to last, in some nations they have disposable ones.) They do not maximize the potential to supress.
Some designs can be virtualy silent however. Not all supressed firearms are cycling semi-autos either. A bolt action firearm can be very quiet because the action is not cycling. Some suppressed semi-auto pistols and carbines have also been designed to allow the bolt/slide to be locked closed so it will not cycle or even move between shots, requiring manual cycling. This allows it to be even quieter. Some do it with a switch others strange things like a multi-stage trigger.
With an extensive multistage suppressor you can actualy achieve Hollywood like suppression (without the goofy sound) which is unrealistic with most calibers.
A decent example of suppression even with a high volume of rounds is the MP5SD with its integral supressor. Not virtualy silent with the 9mm round, but with a .22LR that type of design can be extremely quiet for the volume of rounds. Being essentialy a pistol barrel ballisticly but a full length carbine with most of the length devoted to internal suppression.
Most calibers cannot achieve Hollywood levels of suppression from a realisticly sized silencer, but the .22LR is an exception to that. The cycling of the action can become the loudest part of the process. On designs that allow the action to be kept from cycling they are even quieter, with the noise of the round striking the target the loudest sound of all. The only actual sound from the firearm being the firing pin striking the round.
The most effective silencers also tend to be the most maintenance intensive, and effective for the lowest number of shots and with close tolerances quickly lost from wear. So not practical or ideal for casual shooting. Multiple stages, wipes that wear out, often "wet" requiring refilling with oil or water between a very limited numbers of shots, sometimes with low durability and little longevity while ususaly larger in size than ideal. The most effective possible designs also are integral as that allows the firearm to be designed completely airtight with things like rubber gaskets.
Think of designs similar to the Welrod, but of higher quality and chambered in .22lr, sealed internaly at both ends.
Chambers and containers that capture compressed gases vented to them through one way air valves, never releasing them like a standard supressor can even be incorporated in a design, vhastly exceeding any traditional silencer. No pressurized gas even escapes.
Certainly not what someone spending hundreds on an NFA toy for plinking would enjoy. The gain in suppression would not be worth the loss in simplicity, durability and other areas to the consumer, and as a result such designs are not seen on the market. Who would spend hundreds of dollars for a few dozen suppressed shots between complete rebuilds or required venting of the device? Or enjoy an integraly suppressed firearm with gaskets and wipes that change dimensions and wear out after a limited number of rounds? And with integraly suppressed firearms having the greatest potential, consider there is very few on the market with most consumers purchasing a seperate "can".
All these factors lead to most people with NFA registered suppressors possessing devices that are not maximized for absolute suppression at the expense of other qualities.
They are not all that exists however.
