Interesting experiment... wish my wife was willing to help.
Are you just looking at the sound level on a meter, and it largely instantly pops up and back down?
I have wanted to do somethung similar, but hadn't thought of a good way yet.... I thought people walking above could vary, but a consistent drop of a sledge is interesting.
I have a variety of different set ups in my basement, all with the same Harwood above. I'll probably never get around to it, but now have an idea if I were to do it.
Subfloor (s.f.), r13, 5/8 dw
S.f, r13, clips & channel, 5/8 drywall
S.f., gg, 5/8 dw, r13, clips &channel, 5/8 d.w., g.g., 5/8 dw
And finally, in my theater room:
S.f., gg, 5/8 dw,g.g., 5/8 dw, r13, clips &channel, 5/8 d.w., g.g., 5/8 dw
Now with your test idea, it makes me want to try it out...