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Old 01-09-2007, 01:40 AM
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colbourne
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Default RE: wavescope question

I have used sound recordings and an oscilliscope to analyse aircraft performance.

By comparing the waveforms before and after it passes you you can calculate the doppler shift and the speed of the aircraft.

By using the fast fourier transform feature of the oscilliscope you will see peaks that correspond to the engine rpm ( and also peaks for the various harmonics).

Initially I recommend making some recordings of your aircraft with a sound recording device.
There is a program I think called Winscope which allows your PC to work as an oscilliscope.
Set up a spread sheet with the required values and enter values for your altitude or air pressure which effect the speed of sound.
If you know how fast your engine really is turning it helps in choosing the correct peaks to compare.