Average beamforming in reverberant fields: application on helicopter and airplane cockpits

The aim of this paper is to present the applicability of the Average Beamforming (ABF) as a helpful technique to map acoustic emission for interior noise in which we can assume that sources exist only on the wall, but not in the internal volume. In these conditions conventional Beamforming measurements show disturbing pseudo images in the acoustic maps due to internal reflections that are erroneously interpreted by the algorithm: these pseudo sources are in many cases also stronger than the real one. The proposed procedure consists in carrying out subsequent conventional beamforming measurements from different known locations and combining the relative results statistically: through both the wider “virtual” array obtained and the map of sample standard deviation of single measurement a great improvement both in the resolution and in the map quality is achieved, with a very good accuracy and robustness. The uncertainty of the proposed strategy is also analyzed.