Sensitivity analysis of an equivalent source model for military jet aircraft noise

The noise from a tied-down F-22A Raptor is modeled with an equivalent source consisting of two line arrays of monopole sources and their image sources, to represent the interference from the ground. These arrays, one correlated and one uncorrelated, with Rayleigh-distributed amplitudes, mimic properties of fine and large-scale turbulent mixing noise. [Morgan et al., Noise Control Eng. J. 60, 435-449 (2012)]. The equivalent source modeling parameters (the distributions' peak locations, amplitudes, widths, and the relative phase angle between correlated sources) are selected using Bayesian optimization implemented with simulated annealing and fast Gibbs sampler algorithms. The resulting equivalent source model reasonably predicts the radiated midfield up to 1250 Hz [Hart et al., POMA 19, 055094 (2013)]. In this study, the relationship between the correlated array's peak location and its phase angle has been further analyzed. Although sensitivity analysis of the results reveals non-uniqueness of the model, it also yields additional physical insight in the form of bounds for the dominant aeroacoustic source region as a function of frequency. The far field sound radiation predicted by the equivalent source model for a wide range of frequencies will be compared to measured far-field directivities. [Sponsored by the Office of Naval Research.]