Originally Posted by dgage
I used Roxul Rockboard 60 for wall treatments but OC703 is great too. And I used the Roxul Safe & Sound that you can get from Lowes for the ceiling treatments. I wouldn't use the Safe & Sound in wall treatments as they aren't rigid and could sag.
I used a bread knife to cut the insulation and that worked well.
Regarding size, many recommend leaving an inch between the insulation and the wall so you might build the frame 3" deep and put the insulation near the front to leave the 1" near the wall.
Spot on. That is why I like the OC703. Roxul Rockboard 60 is good stuff too. You want rigid. The people that used the Safe n Sound I think had to put a gap between their front fabric and the insulation to keep it from "bowing" out from the more saggy material. Others put a few dowels in the front and back of the less-rigid insulation to hold it in place, but in my book, by the time you do all that messing around, you could have just paid a few bucks more and got something rigid and used that wasted space from trying to hold the insulation up as an air gap between the insulation and their wall and boosted the performance of the panel.
Check out the links I posted earlier and find a product that looks like it is what you want and call your local home improvement stores to see what they have or can get.
A crash course on the numbers from those links:
The higher the density, generally the lower it will absorb (thickness also plays into this).
The other numbers with the Hz number above them basically mean (again, not detailed, just crash course) how well that material absorbs that frequency. The closer to 1.0, the closer to "full absorption." I know, some numbers are greater than 1.0... This is a crash course, and basically for what we are doing, wee don't care above 1.0 for general absorbers like the panels here.
The NRC is the Noise Reduction Coefficent. Again, 0 is perfectly reflective, and 1.0 means perfectly absorptive. This is more of an "overall rating" based off of a standardized test. So as you can see, some materials have a higher number on the low end, and are typically more dense and thicker to get to those numbers. Air gaps help as well and theoretically a 2" panel with a 2" air gap approaches (fairly closely) to the same real world absorption as a 4" panel with no air gap. This is great since it helps us to keep costs down of course since the 4" panel costs more than the 2" panel (with its "free" 2" air gap).
At home I have a link to a site with a calculator that you can put in the properties of the acoustical material, add other materials (or air gaps) and it shows you the performance comparison on a graph. I can't remember the name of it, and Google isn't being my friend tonight. I travel home tomorrow and hopefully I will remember to find it. I thought that I used it here in this thread somewhere, but maybe that was on a different site...
Anyway, for more details on the numbers, look here: