Helicopter passing overhead

From time to time helicopters pass over our home in Escondido, CA, US. We can hear them coming and hear them leave. I caught several infrasonic tracks of these events, showing incoming and outgoing rotor noise doppler effects. I have attached one for your review. All comments welcome!

David Drake


Hello David, and welcome to our community!

Definitely a great recording of a helicopter pass, the doppler effect is clearly visible, and this is a good example of what other Shakers can look for if they hear choppers around their homes!

Only advice I can give is to zoom back a little more so that the entire waveform/spectrogram can be seen.

Thanks for posting it!

If the helicopter passes pretty much directly overhead, you can calculate its speed from the frequency shift.

I have a small PDF file which describes the derivation of the formula … if you are not interested in how the formula is arrived at, all you need is the result, at the end.

doppler.pdf (76.0 KB)


Chinooks - twin rotor helicopters get really interresting.


Very nice model! Thank you.

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