Your first video is of a 300 blackout. It was designed not by a company really, it was more of a crowd thing. You put a 30 cal round inside a necked out 5.56mm casing. It's designed specifically to be SUPER quiet. But to do that it is a sub sonic round, so it has poor range, and frankly VERY poor terminal damage. Also microphones and modern recording software equalize sounds so it normalizes sound levels; trust me, that gun setup is louder than it sounds in the video. I've shot almost the EXACT same setup. Frankly it still hurt my ears and I wore ear plugs. But it was perhaps the quietest gun I have shot (besides a suppressed .22cal but that's irrelevant.)
Speak of, in your other video they are shooting .22! That is a USELESS round against people unless you're literally holding it to their head and even then it may not work. It's quiet enough without a suppressor that some people shoot it without ear plugs (I can't it still hurts my ears).
You can't trust microphones to accurately give you loudness unless they are specially calibrated and made mics to do so (often used for big expensive symphonies) to do so, and you need several.
That 300 blkout is louder than that video shows.
And besides, all the "mass shootings" are done with rounds designed to kill people, like 5.56mm (or .223cal) or 5.54mm or 7.62 variants. Even suppressed those are all LOUD especially since all those rounds are supersonic so they make a huge noise even after the shot as they create a small sonic boom as they move.
Just recently a company finally made the first commercial shotgun suppressor. It works well actually, but the shotgun is still way loud.
Point is, unless you are shooting .22cal or something like that, low velocity and energy rounds you are going to have a LOT of noise. Go to a range and listen sometime if you don't believe me. I have a lot of experience with this topic.
It's all about energy. For a bullet you either get that from speed, or mass or both. You need enough mass at enough speed to actually make significant terminal damage. Neither 300 blkout or .22cal rounds can do that, the .22 has very low mass and he is shooting subsonic loads, so it's slow as well (regular .22cal (of different variants) are usually supersonic). 300 blkout has mass, but terribly poor velocity. It also doesn't like to act properly when hitting a target; the most lethal rounds either tumble around in the body (such as 5.56mm IF shot from a 16"-22" barrel AND within 300yards of the target), or they create hydrostatic shock from all the energy they dump (you have to be over a certain velocity and energy to do this, the exact number is in dispute); (Usually larger FAST moving rounds do this, such as 300 winmag), OR lastly the round needs to expand and get so big it makes such a large hole that it's lethal (this is what the .45cal was designed for; also a 10mm hollow point, or even better a .50AE round for this; also some .30cal rifle rounds CAN do this, but many don't, they have so much energy they enter and leave the target, which for creating damage is bad, you want the bullet to impart ALL of it's energy in the target, not go through it, that's wasted energy. This is why the 5.56mm(.223cal) is SO effective IF shot out of a long enough barrel and at close enough range, if you do that the bullet literally tumbles like a wobbling top inside the target and is VERY lethal. Shoot it out of a 11" barrel or have a target too far away? It's useless, it punches a tiny hole in and out of the person which is rarely lethal or even that damaging. My father can tell you all about that.)
Enough, you get the idea.
ah so those videos i posted were 140db and that dude just doesn't give a shit/is talking at 140db