Thanks for this demonstration of the discrepancies among different microphone locations when reading frequency behavior in the first 4 seconds. There is no doubt about your data, and I'm greatly impressed by the window into frequency behavior made possible by Pianosense. For us piano tuners, it’s comparable to the world first explored by van Leeuwenhoek with the microscope in the early 1600s.
There is no question about the math either. But as I watched the video, I kind of hungered for a peek behind the curtain at this math. While beyond uTube’s capabilities, there is a way of embedding/retrieving the values for a data point, to be displayed by a mouse click at that point. The bank with my IRA has it on the account’s graph, and map.google does as well. Yes, thank you for uploading the video at 4k resolution, but even on my 20” (dia.) monitor, and with a 4k picture on it (with its available pixels), it’s difficult to visually convert the graph paper background (representing 0.1¢ vertical and 10 millisec, horizontal) into these two values at an actual data point. And others may be looking at these graphs with even smaller displays (or worse, cell phones).
Again, I’m enormously grateful for your invention, and do appreciate the work you put into creating this demonstration. My suggestion here isn’t a concern with the dat and the work to collect it, only the best way to deliver it visually. All the would be required is an embedding the values of the data with three values ( ∆ frequency, the FFT summary of the current time block, and the summary for the previous time block), with the 14 data point for each line (500 msec through 4000). But that would be in another file type, not uTube’s. I know, easy for me to say, not so, for you to do. <G>