Prediction of aircraft flight tracks from noise measurements

A method has been developed to estimate an aircraft’s flight path based on noise measurements at a number of positions within a study area. Two‐second time histories of A‐weighted sound levels were recorded on 38 digital sound level meters (SLMs) distributed by Geo‐Marine Inc. through a mountainous region of approximately 400 square miles. Six of these SLMs recorded one‐third octave spectra. Aircraft pass through this area at low altitude along straight tracks (no turns). Determining the aircrafts position from SLM data is difficult because of the complexity of sound propagation over precipitous terrain and the size of the data matrices. The computational core of Wyle Laboratories’ noise simulation model NMSIM is used to perform the propagation calculations. A least mean square method is used to curve‐fit the flight track to the SLM data. The accuracy of this approach depends on the time intervals of the SLM data, the speed of the aircraft, and the accuracy of the NMSIM propagation algorithms. The NMSIM predicted flight path will be compared to available radar flight track data. Once a flight track has been established, NMSIM modeled time history and spectral data will be compared with measured data.