quantumeffectI don’t think “soundproofing” is the best term to describe what you will achieve by using the Owens Corning product, acoustical treatment is probably a better descriptor. To truly soundproof a space you need to use a combination of isolation building techniques where the two sides of the walls (and I guess you can include floor and ceiling in that) are decouple from one another and building materials that act as “limp mass” (thick vinyl sheet falls into this category). One of the reasons why the unfaced Owens Corning 703 in particular is used in these applications has to do with its frequency dependent absorption characteristics. Compare the sound absorption coefficients at 500 Hz for a 2” layer of the different 700 series products on the Owens Corning product data sheet and you will see what I mean. Why the 703 does what it does with respect to sound (obviously) has to do with what happens when the sound wave hits the surface of the material … and the chemistry and physics of it is quite complicated. So, if you think about it, covering the 703 either by encapsulating in a wall or covering it with material (like a grill cloth) changes it.