Numerical validation of using multisource statistically-optimized near-field acoustical holography in the vicinity of a high-performance military aircraft

Dependence of High-performance Military Aircraft Noise on Frequency and Engine Power

“…Between 50% and 100% ETR, there is an enlargement of the marked 6 dB down region between 400-500 Hz, even when an aliased lobe is not observed downstream. It is probable that the enlargement is an artifact of the spatial aliasing, as it does not follow trends measured from similar full scale military aircraft [31]. Fig.…”

“…Part A discusses the step-by-step procedure which applies the work of Ref [24] to this measurement. Part B is a discussion on the limits on reconstruction accuracy, building on the work of Ref [8].…”

“…A previous study [8] calculated the errors in M-SONAH reconstructions of the F-35B field, which showed that the region of small error is dependent upon the spatial aperture of the holography array. Propagation errors from the holography array to arcs with 19, 29, 38 and 76 m radii were less than 2 dB between = 50 ∘ and = 150 ∘ .…”

“…NAH creates an equivalent wave model (EWM) for the field under examination, which can then be evaluated at any arbitrary point of interest. With a few simple assumptions, reliable estimations -within a certain spatial range of the sampled field -can be obtained to provide a high-resolution image of source and field characteristics [8]. NAH studies on jet noise from high-performance military aircraft have been successful in showing trends across frequency and engine conditions such as source extent and directivity [6,7].…”

Conical Statistical Optimal Near-Field Acoustic Holography with Combined Regularization

“…Both Near-Field Acoustic Holography (SONAH), which provides a new way of better soundfield reconstructions directly by setting up a projection matrix that is optimized for a wave-number spectrum of wave functions with a specific amplitude distribution (scaling), avoiding the truncation effects and winding error caused by DFT of the traditional NAH. Nevertheless, most current methods focus on the statistical optimal planar near-field acoustic holography and only a few studies on the cylindrical sound source for military equipment have been carried out [2][3][4]. When the submarine travels at a low speed, its radiation noise mainly comes from the mechanical noise of the conical stern.…”