Development of a far-field prediction model for tactical jet noise spectra

Semi-empirical models for predicting far-field jet noise radiation are computationally efficient. One historical example is NASA SP-8072 (1971), which couples source sound power spectra with frequency-dependent directivity indices to obtain far-field radiated spectra for rockets. This paper applies the SP-8072 framework to develop spectra for the T-7A trainer aircraft. Data at 38 and 76 m arcs are used to obtain sound power spectra and frequency-dependent directivity indices for four different engine conditions ranging from 36% thrust through maximum afterburner. Application of a ground reflection correction model is discussed. The model is applied to obtain results at distances between 19 and 229 m and the performance of the model is evaluated using measured data. [Work supported by ONR Grant No. N00014-21-1-2069.]