As I told you before, the sound attenuation is 3 db at 1 meter (38").
At 7" (your example) is a wooping 1 db less, for an 80db 7 iron is under 1% error. I know for sure that my PRGR is not that accurate, even my skytrak isn't that accurate. For a FREE unit seams to be promising if you can't afford a speed meter.
Again, you are swinging in the same spot, over and over again in the same session. Phone position is the same , background sound is the same, environment is the same. The only difference is the peak sound you produce when you whoosh the club.
You need to do a lot better to discharge an idea.
I'm not real familiar with Raynor, so I looked at the Golf Club Atlas article. It was interesting to see Dye essentially copy an "old" design, but I imagine that almost all current designs are based at least partly on the work that has come before.