Helicopter approach and departure - Doppler Effect on RS1D


Here’s a great demonstration of Doppler Effect showing the approach and departure of a helicopter. The view is spectogram and shows a clear frequency decrease at flyover. This was recorded using a RS1D 4.5 Hz vertical geophone. The main train goes from about 28 Hz to 12 Hz. You can see a higher order train coming down from 50 HZ right at flyover.