Helicopter and Turboprop Aircraft signatures

Comparing Flightradar and ShakeBoom activity today. Followed a rescue helicopter from Wellington and the Boom heard it approach and pass over. Looks like it emits approx 30Hz on approach and overhead then drops down to 25Hz as it flys off. Also the Air NZ ATR turboprop at 14,000 ft was emitting a similar but much shorter duration Doppler signature. The noise to the right of that is the dog that decided to bark for no apparent reason - now I know what sets her off for random reasons - I should be able to correlate her barks to Flightradar :slight_smile:


Helicopters direct the pulses from their rotors downwards - which rattles windows, walls etc. Because of this, they seem to be detectable further away that turbo-prop aircraft which are directing their prop pulses horizontally.

You might find this document useful.

doppler.pdf (76.0 KB)


Did not manage to capture a clear/clean turboprop signature yet (even if the local airport is close, but I am not on any approaching route), so this is very interesting!

Now that I know the local airport flight schedule I am hoping to catch one of the commercial regional flights. It’s also weather dependant as they don’t always take off north across my area.


They need to be fairly low and pretty much overhead. Most of the sound is (relatively) high frequency, so doesn’t show up.