Used these to build some acoustic panels. These were specifically placed in the corners of the room to act as base traps. Bye-bye long base reverb and boominess! I used wood that was 3" wide so that there was a .5" air gap on each side for improved acoustic absorption. I tested Muslin, Microsuede, and Guilford of Maine acoustic fabric 14.4 oz. weight per linear yard, 17 x 15 construction (thread count per inch). The MicroSuede was the least acoustically transparent, the Muslin more acoustically transparent, and the Guilford of Maine was the most acoustically transparent (but cost $$$).
I haven't made my sound proofing panels yet but, the product does appear to be very suitable for my purposes. My only issue is with the packaging. It was very flimsy and did not protect the panels from damage in shipment which, of course, is the purpose of packaging. Yes, I might still be able to use the damaged panels. My expectation was not to have to find a creative way to use damaged panels.