Passive estimation of aircraft motion parameters using destructive interference between direct and ground-reflected sound waves

An aircraft emits continuous broadband sound energy that arrives at a microphone located above the ground via a direct path and a ground-reflected path. A time-frequency analysis of the sensor output shows a two-dimensional interference pattern in the time-frequency plane, where the distributions of minimum energy correspond to the temporal variation of the destructive-interference frequencies. In the paper, a model is developed to describe the temporal variation of the destructive-interference frequencies for an aircraft in level flight over hard ground. Based on this model, a nonlinear least-squares (LS) algorithm is formulated to estimate the motion parameters of the aircraft. Computer simulation results are presented to validate the model and to verify the effectiveness of the nonlinear LS algorithm.