Intensity analysis of the dominant frequencies of military jet aircraft noise

Abstract

Acoustic intensity measurements of the F-22A Raptor are analyzed as part of ongoing efforts to characterize the noise radiation from military jet aircraft. Data were recorded from an array of microphones and an attached tetrahedral intensity probe at various locations to the sideline and aft of the aircraft. Recently, techniques such as coherence, similarity spectra analyses, and near-field acoustical holography have indicated a peak-frequency region comprised of two maxima (not accounted for by current jet noise models) that have very different radiation directionalities. Acoustic vector intensity is analyzed as a function of frequency to further assess the behavior of this double-peak phenomenon. In addition, a simulation using an equivalent source model with two mutually incoherent, directional line arrays yields numerical intensity results that exhibit the same trends as the measured intensity. The results provide further evidence that high-performance military jet noise contains a double spectral peak in the maximum radiation direction that is not present in laboratory-scale jets. [Work supported by ONR].