The use I wanted it for is for a server room, so I can't say if it makes a difference in recordings or video calls.

Inside there are 10 servers, 2 for backup with x16 disks and 8 running programs, etc., and a professional UPS. All of these create a noticeable noise from the fans. I haven't covered all the walls and I don't have a decibel meter, but there is a noticeable difference in the noise from outside and inside. I have placed them in groups of four and covered one wall with the door facing the offices.

They do their job very well and I will get another set to put on the remaining walls