Analysis of reports and crackling sounds with associated magnetic field disturbances recorded during a geomagnetic storm on March 7, 2012 in southern Finland

Audio- and magnetic field signals were recorded during a geomagnetic storm on March 7, 2012, on open fields at Karkkila, approximately 70 km north of Helsinki by using a Zoom H4n recorder. Almost 90 distinct sound events like short claps, loud reports, or even a crackling sound were recorded. The paper describes the methods used and the results obtained in the audio- and magnetic field signal analysis. Relationship between the instances of the sound events and the geomagnetic activity is described. It is shown that the spectral properties of the crackling sound and the reports are similar. The challenges in finding connections between individual sounds and the corresponding magnetic field fluctuations are demonstrated and discussed.