I built a system a few years ago as part of my undergraduate degree that could localise aircraft using microphone arrays and acoustic beam forming. My primary

I built a system a few years ago as part of my undergraduate degree that could localise aircraft using microphone arrays and acoustic beam forming. My primary sources for information were books on SONAR. The system worked in real time but also stored all the raw data so it could be processed again later if you wanted. I also had some fun trying to identify the aircraft based on frequency content and details on engine speeds / blade counts from Type Certificates.