Comparison of holography, beamforming, and intensity-based inverse measurements on full-scale jet noise sources. Part II: Experimental results

Abstract

Targeted reduction of high-amplitude jet noise is facilitated by accurate source imaging and sound field prediction models. To provide guidance for future jet noise reduction efforts, near-field acoustical holography, beamforming, and acoustic vector intensity-based inverse methods (AVIBIM) have been implemented in efforts to measure and predict full-scale high-performance aircraft noise sources. Patch-and-scan array measurements were taken in the near-field of a tethered tactical aircraft. From these data, equivalent source reconstructions are calculated using each method at multiple frequencies, and the source results are then propagated outward and compared with benchmark locations in the mid and far fields. The frequency ranges where each method’s reconstructions predict the measured sound pressure levels are identified and guidelines are provided for the design of measurements to optimize source reconstructions. These results are compared to those obtained in the numerical study (Part I) of this two-part investigation. [Work supported by USAFRL through ORISE.]