INFO: This eight second video is extracted from a set of test recordings that have been collected within the Auroral Acoustics project (2000-2012). During this time period high-quality audio recordings were made during approximately 100 geomagnetically opportune nights at different locations in Finland. These recordings form a database that is half a terabyte in size. This short clip has been selected from some video recording experiments that were performed during some nights simultaneously and independently of the main activities.
Even though this video was recorded in 2004, the clap sound (at 8 and 31 seconds) was discovered only in May 2012 when the material was copied from DV tapes to disc. This is the first time during our project history when a clap sound has been recorded simultaneously with three different microphones. Due to the experimental nature of this material, it may not be useful for scientific analysis.
However, we were lucky to encounter a similar situation again in September 2011. Three microphones registered similar clap sounds and now the developed methodology allowed for a closer analysis of the data. It produced a surprising result: the sound source was geometrically calculated to be in the open sky about 70 meters above the ground. A preliminary report of this phenomenon has been presented in the ICSV19 proceedings (Vilnius, Lithuania, July 8-12 2012),
The result opens up a new phase in the Auroral Acoustics project. In order to celebrate this finding and to evoke discussion on the topic -- before the 2013 solar max -- we made a decision to publish this short video clip. Also, with this experimental video, the authors would like to thank the audience in Finland for their auroral sounds observation reports that now number over 300 cases with the most recent ones made during the spring of 2012.
Video by: Unto K. Laine and Aalto University Communications / Mikko Raskinen