Design of microphone phased arrays for acoustic beamforming

The design of a microphone array affects the performance of beamforming algorithms in the localization and evaluation of acoustic noise sources. This paper addresses a circular phased array design for near-field aeroacoustic measurements in a closed-test-section wind tunnel. Microphones were distributed in rings and occupied an equal aperture area-each ring could have a different number of microphones. The array performance was evaluated through the dynamic range and array resolution given by the beamwidth. The array designed for the exploration of the novel approach had 112 microphones and 950-mm aperture. In comparison with classical designs, also optimized for the same number of microphones and aperture, the approach provided the best array resolution and a high dynamic range level almost uniform over the frequency range of interest (800 to 20,000 Hz). Microphone shading was also assessed for improving the array performance, and the employment of only the outermost microphones (the innermost ones were shaded) reduced approximately 40% the array beamwidth.