1 Department of Mathematics, Technical University of Denmark2 Applied functional analysis, Department of Mathematics, Technical University of Denmark3 Department of Electrical Engineering, Technical University of Denmark4 Acoustic Technology, Department of Electrical Engineering, Technical University of Denmark5 Department of Applied Mathematics and Computer Science, Technical University of Denmark6 Technical University of Denmark7 Brüel & Kjær A/S
The mapping of noise is of considerable interest in the car industry where a good noise mapping can make it much easier to identify the sources that generate the noise and eventually reduce the individual contributions to the noise. The methods used for this purpose include delay-and-sum beamforming and spherical harmonics beamforming. These methods have a poor spatial esolution at low frequencies, and since much noise generated in cars is dominated by low frequencies the methods are not optimal. In the present paper the mapping is done by solving an inverse problem with a transfer matrix between the volume velocities of the sources and the measured sound pressures at the microphone array. This is an illposed problem and therefore regularisation have to be applied when the transfer matrix is inverted in order to give good results.