Traveled down the road of "acoustic materials" that at first bluster seemed to be the way to go. However, once the overall price hits you upside the head you realize that cotton...
Here is what AI states:
Yes, sound can travel through cotton, but it also absorbs sound effectively. Cotton's porous structure and soft, fibrous nature allow it to trap and dissipate sound energy, making it a good acoustic material. In other words, sound can pass through cotton, but it also loses energy and is not reflected as strongly as it would be from a hard surface.
As Dave and Troy stated, you can create a dead room by using too much. This is especially true if your room is smallish. A big room will require quite a few of 703 baffles before the room gets to that point.
There has been a fairly large uptick in commercial entities (restaurants, office buildings, etc) using noise barriers as privacy is becoming more important, even in public settings. Perhaps some of it started in the covid era where public places realized people do not like to listen to other people talk..or maybe it's they don't like what other people say.