Noise Cancellation of Multichannel Magnetic Resonance Sounding Measurements with Wiener and Adaptive Filters

Magnetic resonance sounding (MRS) is a unique and promising hydrogeophysical technique. Due to its ability of providing a direct estimate of the water content and estimates of the porosity in the subsurface, MRS has the potential of being a great team player in the field of hydrological prospecting. However, the MRS measurements suffer from a low signal to noise ratio due to the signal being inherently weak and the susceptibility to electromagnetic interference. The low signal to noise ratio currently impedes the applicability of the technique, particularly in urban areas. In recent years the development of multichannel MRS has opened up new possibilities for advanced noise cancellation methods. Before multichannel MRS can realize its full potential robust and reliable methods for noise cancellation must be developed. In this work we compare two noise cancellation methods: The multichannel Wiener filter and a multichannel adaptive noise cancellation filter. The comparison is performed on noise records from a multichannel MRS instrument with or without synthetic signal added. Our results show that adaptive noise cancellation performs better than the Wiener filter for both pure noise removal and for recovery of the parameters of the synthetic signal.