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      07-26-2013, 07:35 PM   #86
swamp2
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Quote:
Originally Posted by bradleyland View Post
My analysis shows a result that's closer to 7400 RPM. If you download my files, you can open the .aup files with Audacity (it's free). Running spectrum analysis on the audio just before the upshift always gives me values closer to 330 Hz, not 350-360 Hz. Not sure why exactly.

Full write-up: http://upload.bradlanders.com/bimmer...ound-analysis/
Completely agree.

Although 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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Last edited by swamp2; 07-26-2013 at 09:11 PM..
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