The present invention introduces a method for adjusting interference signal estimates provided by multi-channel biomagnetic field measurements. A so-called Signal Space Separation method (SSS) is applied in the calculatory analysis of the measurement signals, providing for the division of the sources causing the fields in objects of interest and external interferences. When the signal basis representing the interferences has been estimated, this interference signal estimate is adjusted by measuring the fields without the object to be measured and without changing the sensor assembly. Interference components obtained in this manner are analyzed in such a way as to include only the most significant interference components. In addition, it is taken into account that only those forms of interference of the measured interference components are included which are not yet present in the calculated SSS model. Finally, an adjusted interference subspace is formed, by means of which signal processing and the analysis of the useful signals can be continued. In the invention, the incorrectly functioning signal channels can also be taken into account and equated with the external interferences. In one embodiment, the above-described process can also be performed for the signals of the internal basis, i.e. for the signals of interest.
