Back in January I wrote about ice yowling and other geological sounds. One of the commenters told of hearing sounds in conjunction with the aurora borealis or northern lights: "a very distinct hiss like grains of rice sliding on a teflon cutting board. It's very faint and requires a still night and a fairly active display to hear but it is awe-inspiring."
One thing that has puzzled me about auroral sound is that while the lights are far up in the atmosphere, around 100 kilometers, the sounds match the lights. It's not like lightning and thunder, which are clearly separated in time because of the difference between the speeds of light and sound. One explanation I always entertained is that the sounds are generated inside the ear or the brain by the aurora's electromagnetic fields. But a Finnish team set out microphones on a night of strong auroras and recorded soft sounds that they triangulated to about 70 meters above the ground. They presented their results this week at the 19th International Congress on Sound and Vibration in Vilnius (read the press release). A video presents a sound like a whipcrack. I love this stuff.