@mrehorstdmd Just to note that using an accelerometer, analyzing and getting consistent results is far more difficult that just using a microphone, and I'm not sure if in this case the results would be more relevant.
But if you want to try anyway, I will look forward to your setup and results.
Also if you are using acelerometers, get the resonant frequencies directly, you just need to use an impulse function, just hitting in this case the extruder with a small hammer or something similar.
About Audiacity, that was what I was thinking about but I'm not sure if it can be used that way, if I recall correctly we were using Matlab programs. Maybe you can check in Octave, the opensource alternative to Matlab