Getting a PhD is expensive and unless you have to have the union card not worth while. I only went back because I had *no* training in seismology at all. I'd been hired into a job because I had a degree in geology and had taken Diff EQ. But I thought DSP was super cool and I wanted better than I could do on my own with a stack of books. When I was hired I was promised several months of training in Tulsa where Amoco had their labs, but I worked for 18 months before I got my only 2 week course. Meanwhile I had to do the stuff we are talking about and more. The only thing that saved me was my boss had an MSEE and I had a ham license. He had come from the labs where he wrote a lot of the DSP codes. So he could translate geophysics speak into radio speak. I also knew optics very well and so all my knowledge of the wave equation was very important.
The thing that *is* important about the PhD is acquiring the ability to master a subject for which you have no prior training. I'm immensely proud of having been able to learn sparse L1 pursuits on my own. I won't claim to have mastered it because I've not found anyone to test my knowledge against except at a fairly superficial level. But I do understand it well enough to know that most of the 3000 pages I read are irrelevant to actually applying it. Most of it is just the logical proof that it works and why. There is a similar amount of verbiage that was developed to prove that the Fourier transform worked. As with Heaviside's work, it took the mathematicians a lot of time to develop the logical justification.
Get a couple of these to play with (just in case you break one):
https://www.stewmac.com/Pickups_and_Electronics/Pickups/Violin_Pickups/Schatten_Soundboard_Transducer.htmlThey are very fragile, so epoxy them to a thin, ceramic disk magnet the same diameter or slightly larger. The neodymium magnets would be too strong. The construction is a thin brass sheet with a pizeo sensor bonded to it and foam to reduce feedback on the top.
One possibility would be to remove the foam and cast an epoxy case with an eyelet. An actuator could lower the unit on a string until the magnet grabbed. Leave the string slack while running the test and then pull it away.
They are made as light as possible so they don't dampen the guitar top. That doesn't matter in your case. That is specific to the application on an acoustic guitar. There are sensors with broader response, but the prices start going up quickly. These are cheap enough to play with.
I glued a small spruce disk to the sensor for reinforcement per factory instructions. They supply butyl tape to attach them and if you try to move one without the spruce reinforcement it will break.
The first photo shows the experimental setup. I took a scrap tweeter with a busted cone, stripped off the remains and glued a spruce disk to the end of the cone. Then I swept it with my 33622A from 20 Hz to 20 KHz. The first scope shot shows the input and the output over the full range and the 2nd up to about 8 KHz. The amplitude variation of the input is presumably just mismatch between the 33622A and the inductive load. As the reactance rises, the voltage differential across the terminals should go up. At the time I didn't realize that the 33622A had a high impedance output option so this was a 50 ohm source resistance and the apparent ramp is just the voltage divider effect of the load.
One of the applications of sparse L1 pursuits is "blind source separation". Or in simple terms, with a few microphones scattered around a crowded cocktail party, isolate any speaker in the room. It's all a question of setting up the proper A matrix for the problem. I mention that because with a pair of microphones there is a potential to diagnose the exact fault location and thus speed up the rework and collect SPC data.
A box made up with sides in the form of drywall - soft foam - acoustic tile with the drywall on the outside and doors at each end that ran in rails vertically would reduce ambient noise a lot and be very amenable to full automation on a fast moving assembly line.
Clearly what is needed is a "good enough" solution ASAP. You're already very close to that. The major hurdle of the fundamental mathematics is done. So now it's a question of engineering an implementation which meshes well with the production process. Edison demonstrated how you do that. You try a lot of possible solutions to a problem.
Have fun and show me some pictures.