I actually run an audio recording studio, so I can speak with some authority on this subject.
First off, there is a big difference between sound absorption and sound isolation.
Sound absorbing materials work in relationship to the thickness of the material. In other words, the thicker the material, the lower the frequency that can be absorbed. For example, in order to absorb bass frequencies when recording music, I use acoustic panels that are at least 4-6 inches thick. Anything thinner, and all you are absorbing are mid to high range frequencies. These are used to balance the frequency response of a room and reduce first-reflection echos.
Sound absorbing blankets (which are really not very different from the dense blankets that movers use when packing up furniture in a moving truck), are relatively thin, so they are limited in their use, but can be effective in removing that echo-y sound bouncing around the room, resulting in a cleaner, more intimate sound. I'm sure you've seen some vids where it sounds like they were filmed in a warehouse due to all of the ambient noise, the sound blankets will help this. (BTW- you don't need to cover the entire room, but a few strategically placed ones will make a difference)
They won't make the room silent, or reduce the sound of your... subjects (victims?), they simply will cut down on the echos that would otherwise distort your sound. So, the blankets would probably help the sound on your videos. But they really won't do much as far as isolating the sound within your room (i.e. keeping the sound away from your neighbors).
They'll help....
some, but remember, the sound will also travel through the heating/air-conditioning ducts in your house and escape through the cracks under doors, as well as vibrating through the walls themselves.
BTW, that product you were referring for construction, is called
sheetblok, and that is only a part of the equation.
And please, please, please, DO NOT use egg cartons!!!!!!!!!!!!!
(also, don't use one of those "egg-crate" foam mattress pads on your walls)
That is a fire-hazard / death trap waiting to happen!
Plus, remember what I said about frequency absorption being related to thickness of the absorbing material? Think about the thickness of an egg carton... yeah, acoustically they are just shy of worthless.
That was probably more information than you were looking for!
🙂