Source terms corresponding to Goldstein's generalized acoustic analogy are computed from a high-fidelity simulation of a supersonic jet issuing from a rectangular nozzle with chevrons. Simulated data are validated against experimental data. We investigate the theoretical underpinning of reduced-order acoustic source models by testing the assumptions of quasi-normality and statistical axisymmetry. It is found that the flow is not quasi-normal in the axial direction but is quasi-normal in the transverse directions. Our analysis also shows that the flow is locally statistically axisymmetric close to the edges of the flow but not near the center. Fourth order correlation statistics are fit to previously used acoustic source models originally developed for axisymmetric jets. This thesis performs a detailed analysis of four different models: the Gaussian, moving-frame, fixed-frame, and modified-distance models. The latter three models are found to be similar in accuracy, while the Gaussian model is found to be a poorer fit.