User blog comment:Nerdfighter88mph/Artifact Challenge 2/@comment-3270170-20130625162854/@comment-5995342-20130627021540

It's not Raijin's drum, these explosions sound more like bombs from the 40s. And I the only group that may be it is a group of people that think they are fighting in WW2. So my guess is a Blitz related artifact.