Interesting sound. I would have guessed a Wild West performer was practicing with a bullwhip while also vacuuming. But no. That sound is (apparently) produced by the aurora borealis, the northern lights.
Since 2000 researchers at Finland's Aalto University have been collecting audio as part of what's called the Auroral Acoustics project. Folk tales have long held that the lights also produce odd sounds, but the claims were hard to prove. And some (researchers) thought that any noises produced by the energetic particles that cause the light show would be far too high in the sky to be heard on the ground.
But the latest results indicate that at least some sounds are produced very close to the ground. A setup of three ground-based (microphones) allowed researchers to estimate that the sounds occur perhaps just 70 meters up. The results were just (presented) at the International Congress on Sound and Vibration in Vilnius, Lithuania.
More information about the sounds of the northern lights could lead to a more complete understanding of the phenomenon. So if you see an aurora, keep your ears open.
