Noise mapping inside a car cabin

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.