An experimental and numeric investigation towards a reliable acoustic pressure level estimate using phased-array techniques

The use of phased array techniques has become an ubiquitous tool for noise source localization, but some skepticism still remains in which regards sources level quantification. In the attempting of contributing to fill the knowledge gap in this particular issue, this study focuses on the analysis of fundamental beamforming formulations and assesses experimentally their inherent ability to determine the sound pressure level emitted by a single testing source. Acoustic measurements were performed by using a wall-mounted microphone array installed in a closed room equiped with foam to simulate an anechoic facility. The source level obtained from both conventional and orthogonal beamforming techniques showed a remarkable agreement compared to the microphones average auto-spectra. The study also discusses a supposed new steering vector formulation, which was obtained heuristically and applied to beamforming. This formulation was compared to two other different ones using two different array geometries. Tests were based on a monopole beamforming analytical model. The study presents and discusses numerical and experimental procedures required to achieve an accurate source level estimation, which can be applied to general-purposes aeroacoustic measurements.