Quote:
Originally Posted by swamp2
Completely agree.
The low pass filtering, fourier techniques and stereo vs. single channel stuff are all completely irrelevant, they just don't affect the answer. My error was recording through speakers rather than internally. Even trying to repeat my process showed considerable error. After switching to recording with Soundflower the shift burble was much more recognizeable visually in the traces. I also got much more recognizable peaks in the spectral results. I agree the observed frequency is right around 330 Hz perhaps with a worst case range of about 325-335 Hz. Thus with a Doppler correction from 90-97 mph this provides an rpm range of about 7250-7550 (with rounding to 50 rpm).
This is how science works - basic peer review. Thanks for keeping me on my toes. I will revise my OP in a way to not hide my shortcoming and I'll give you the credit due.
Thanks!
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^^^ THIS is a class act and that which keeps this forum valuable to all the rest of us! I have a degree in engineering (from way back) and this sort of stuff makes my spine tingle.