Beamforming in the Time-domain using 3D-microphone arrays
Gunnar Heilmann, Andy Meyer, Dirk Döbler · 2008
Traditional beam forming systems with planar microphone arrays do not give comprehensive information about the sound sources inside a cavity such as car interior or an office room. Acoustic measurements inside any cavity are mostly conducted with a few number of microphones. By this means it is possible to gain information about frequencies, orders, sound pressures. However, a space selective analysis is nearly impossible and it is not feasible to find multiple sound sources positions in space in a practical way. Therefore, the constituents of the Acoustic Camera of the GFaI were extended by a spherical, acoustically transparent and omni directional array. A new option is to map onto a common 3D-CAD-models of the object of interest, for instance an office or class room. First of all the advantages and disadvantages of 2D- and 3D-mappings will be discussed in the paper. Furthermore, the important issue of positioning an array at first in the coordinate system of the 3D-model and second in the actual cavity which is to be measured will be addressed. The paper discusses the geometric and acoustic properties of microphone arrays which are applicable for complete 3D-measurements and mappings of cavities. A practicable way of determining the array’s position and direction related to the measurement object will be proposed. Several practical experiments will be displayed to underline the methods capability and reliability.