Obtaining acoustic intensity from multisource statistically optimized near-field acoustical holography

Abstract

Multisource statistically optimized near-field acoustical holography (M-SONAH) improves the field reconstruction process by directly incorporating into the pressure propagator types of wavefunctions that correspond most closely to the source geometries of interest [A. T. Wall et al., J. Acoust. Soc. Am. 137, 963–975 (2015)]. The M-SONAH method has previously been used to localize acoustic sources in a full-scale jet engine plume above a rigid reflecting plane by adding a second set of cylindrical wavefunctions corresponding to the image source [A. T. Wall et al. J. Acoust. Soc. Am. 139, 1938–1950 (2016)]. Here, M-SONAH theory is extended to obtain the vector particle velocity and, by extension, the acoustic intensity. Discussed are two examples that relate to the full-scale jet noise-with-image-plane reconstruction problem: (1) a Gaussian line source with image and (2) a jet-like wavepacket and image, with hologram geometry identical to that of the full-scale experiment. The results from both examples reveal intensity errors less than 3 dB and 10 degrees within the top 20 dB of the reconstruction region. The results also suggest that intensity reconstruction magnitudes less than those obtained at the measurement aperture edges should be discarded. [Work supported by ONR.]