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Modal beamforming using planar circular microphone arrays

Authors Zaunschirm, M.
Year 2012
Thesis Type Master's thesis
Topic Audio Signal Processing
Keywords audio recording
Abstract Beamforming denotes the discrimination between signals based on the spatial location of sources. Whilst conventional beamforming algorithms directly operate on the sensor signals, modal beamforming approaches use directional modes that are obtained by decomposing the wave field into orthogonal solutions of the acoustic wave equation. Spherical arrays are more generic as they allow for higher-order resolution and for steering a designed beampattern to any direction in the three-dimensional space without altering the shape. For applications where a full spherical array is uneconomic or redundant the use of circular arrays is feasible. As conventional circular arrays lack control of the beampattern in the vertical array plane, this thesis deals with the design of a planar circular microphone array that allows for steering beams towards both the horizontal and vertical array plane (but with changed shape). In this context, the decomposition into the directional modes is explained based on measurement data and based on an analytical model. Further, the general concept of modal beamforming is outlined and the generation of optimized beampatterns is derived based on linear pressure gradient microphone arrays.
Supervisors Zotter, F.