With the exception of the thinner Sonic Barrier (might need to retest), the damping for all materials tested is very comparable from 300 to 600 Hz.
View attachment 392871
Can see very similar results from the 600 to 1200 Hz with the major standouts being the thicker Sonic Barrier (red trace) and No Rez (yellow trace). Sonic Barrier does better from 100-1200 Hz and NoRez does better from 1200-2000 Hz. Much above 2000 Hz the differences start to lessen as the early frontrunners show some variability. This view is pretty complex, so here is a simpler one that may help...
View attachment 392879
This the baseline with NoRez and Sonic Barrier and the purple trace adds the cotton blanket. As I mentioned, doubt that much above 1200 Hz or so is audible with a rear port. So might argue that the cotton seems the best value. Will need to add some frontal measurements to see if there is some other difference. Before I do, will also look at some often-applied combinations to see if they yield any better results. Am not sure whether the denim advocates are lining the walls or shredding it as fill. If there is major interest, maybe will test the Sonic Barrier but is not inexpensive (although cost per square inch is much better).