Flight parameter identification from cepstrum tracks

Abstract

By using a single microphone located above the ground, it is possible to determine the flight parameters of an aircraft fly-over. This technique utilises the asymmetry of the Lloyds mirror rings (LMR) that have been converted into a primary rahmonic in the cepstrogram of the acoustic data. Unlike previous techniques, the spectrogram is not needed. The cepstrum data are automatically processed by a hidden Markov model tracker that provides input to the flight parameter estimation stage. The Levenberg-Marquardt optimisation procedure is then applied to derive the aircraft speed along with the time, horizontal distance and height of the closest point of approach. Reliable cepstrogram estimates are obtainable when at least three LMR's are present in the spectrogram data.