Simple-source model of military jet aircraft noise

This paper describes a method for determining a semi-empirical, equivalent simple-source model that accounts for the sound radiation in the vicinity of a high-performance military aircraft. The characteristics of the equivalent source are guided by previously reported observations of jet noise, namely that the strengths of the partially correlated sources are distributed asymmetrically. The parameters of the equivalent source model are chosen to reproduce the data recorded on large planar apertures in the near-field of an F-22 Raptor. First, the location of the dominant source region for a given frequency is found by matching the orientation of the interference nulls in a sound pressure level map. Second, the relative contributions of the correlated and uncorrelated portions of the equivalent source are chosen to replicate the directionality and extent of the sound field. The source characteristics are selected based on the data at one measurement plane but are able to approximate the radiation at other near-and mid-field locations. The method is used to find equivalent sources at several frequencies and different engine conditions. (C) 2012 Institute of Noise Control Engineering.