Fig. 2

Array processing results for all versions of the data using dtkPMCC. PMCC results shown are using the INFERNO filters. Each pixel is plotted and colored by calculated back azimuth, the known back azimuth of the source, 82°, is yellow in color and the average back azimuth of the microbarom, 220°, is blue. The frequency axis is plotted on a logarithmic scale. The array processing results are dominated by the microbarom but while the event is not overly obvious using the raw data, it became clear on the three types of pre-processed data. To evaluate the differences between the different results, we grouped the output into 5° azimuth bins and then we consider pixels within the bins on either side of the expected back azimuth. For the raw data processing there are 152 pixels in 5 families, while that number increases to 1369 pixels in 16 families, 1967 pixels in 20 families, and 1051 pixels in 11 families, for the individual noise reduction, batch noise reduction and batch adaptive runs, respectively