A Three-Dimensional Microphone Array for Wind Tunnel Application

The positions of microphones in arrays are usually distributed two-dimensionally either in a plane or on the surface of a cylinder or sphere. For such two-dimensional arrays, the determination of a point-spread function is well-known and can be used within a certain boundaries to optimize arrays in terms of minimizing the effect of side lobes in the beamforming maps. In contrary to the usual two-dimensional array configuration, the present paper outlines the development and implementation of an array for wind tunnel application where the microphones are distributed three-dimensionally. The microphone positions within this array are optimized to reduce the side lobes in three-dimensional space. This approach of using an ab initio three-dimensional distribution shows significant advantage over the combination of multiple planar arrays to form a quasi-three-dimensional microphone arrangement. The technique has been applied to wind tunnel measurements to emphasize the benefits of this approach. In the final paper, results will be shown and practical difficulties like the exact positioning of the microphone within the three-dimensional space will be discussed.