1 Department of Electrical Engineering, Technical University of Denmark2 Acoustic Technology, Department of Electrical Engineering, Technical University of Denmark3 Department of Mechanical Engineering, Technical University of Denmark
Recent studies have shown that the localization of acoustic sources based on circular arrays can be improved at low frequencies by combining beamforming with acoustic holography. This paper extends this technique to the three dimensional case by making use of spherical arrays. The pressure captured by a rigid spherical array under free-field conditions is used to compute the expected pressure on a virtual and larger sphere by means of acoustic holography. Beamforming is then applied with the pressure predicted at the virtual array. Since the virtual array has a larger radius compared to the one of the physical array, the low frequencies (the ones with larger wavelength) are better captured by the virtual array, and therefore, the performance of the resulting beamforming system is expected to improve at these frequencies. The proposed method is examined with simulations based on delay-and-sum beamforming. In addition, the principle is validated with experiments.