An acoustic beamforming array design method for spatially restricted experimental facilities

Experimental facilities for aeroacoustic tests can contain large apparatus and supporting structures. This can impair the design and/or installation of an acoustic beamforming array that requires significant space and, in most cases, a clear line of sight between the array and the acoustic source. To alleviate this issue, previous studies have populated portions of spiral-based arrays over usable areas to best utilize the available space. This paper aims to numerically compare the performance of this array design method with a recently published method, called the Adaptive Array Reduction Method (AARM). The AARM simulates a large initial array and iteratively reduces the array to a desired number of channels by removing the channel based on sidelobe and main lobe criteria. The AARM and a spiral-based array design method were applied to a hypothetical room containing several obstructions, and a non-square area at NASA Langley Low-Turbulence Pressure Tunnel. In both cases the AARM outperformed the spiral-based array designs in terms of main lobe width and maximum sidelobe level and in some cases the main lobe distortion. To experimentally verify the design of AARM arrays over irregular areas, experiments were conducted at the Southern University of Science and Technology in an anechoic wind tunnel, using both a speaker source in zero-flow conditions and a NACA 0012 airfoil placed in uniform flow. The performance of the AARM arrays created over irregular areas were compared against an AARM array designed over a square area, revealing little to no decrease in performance in terms of source localization and sidelobe distributions in the source maps. The AARM has been shown both numerically and experimentally to be a suitable method for designing acoustic beamforming arrays in a spatially restricted experimental facility.