Doppler Velocity & RPM Using Microphone

[PhilLin]

Hi, Folks! This subject came up in the Jets forum but dialogue was not sustained, so I hope this is a more suitable forum for it.

The idea is to use a laptop with mike input to capture the approach & departing sound from a flying model to analysize for prop or fan rpm and flight speed of aircraft. Would sure appreciate anyone with sound recording expertise to explain the format & data in a wav file. I suppose we could plug the analog sound output into an oscilloscope, but sure would be nice to extract time series data for FFT analysis or some other short cut digital technique. Any takers? My apologies if this has been covered in previous threads.

[Paulus]

Hi,

Here's a link that describes it pretty good.
http://www.philsrcworld.fsnet.co.uk/speed.htm

greetings,

Paul Ravensbergen

[PhilLin]

Many thanks, Paul! I'll look right into it.

[Haldor]

Its been a while and I'm on a new PC so I dont have the progs on hand but here is what i used for just that.

1 - Fly the plane and have a buddy film the flight. Make low passes and have your buddy as close to the plane path as possible.

2 - Import video to your PC and take a low pass and export the .wav of that sequence.

3 - Then analyze the file to find F(in) and F(out)

4 - I found and used a Excel spreadsheet to input the F's and got out a speed reading.

So basically all you need is video of the flight and you can determine speed later.

[PhilLin]

Thanks for your response, Haldor!

I downloaded the analyzer files from philsrcworld link above. Nate W also responded & pointed me to site for the .wav format in the jets forum. I'll give these a try.

BTW, I like your jets. Keep posting.