That's for a 5.93 in2 circular piece as per the standard test.
I see this basically as a filter in a pipe. We have pressure and and velocity measures. Can we determine from that some kind of coefficient for that material that can be used to evaluate what the flow would be past the second layer...
I have a fabric from a windshirt testing at 40 CFM under ASTM D 737 (125 Pa). I am interested in understanding what would happen to air velocity if two layers were stacked and tested. Next, how would the results be affected by an air gap between the two layers?