Tuesday, December 8, 2009

Radio Spirits

Alright, so I lied when I said I'd be updating this blog regularly while I was up North. But I'm back in Montreal and will continue to share interesting sonic events I experienced in Inukjuak, Nunavik.

One of my favorite field recordings was taken outside the Pigiursavik school where I was holding the workshops. During one extraordinarily windy week, I stood outside the school at night and heard these really eerie sounds. Sort of a varying melodic motif sung in a minor key. These wind songs would go on for hours. To add to this, the aurora borealis was starting to form in the skies that week. So this was quite a cinematic experience. I was reminded of Jim O'Rourke's haunting soundtrack to the Peter Mettler film Picture of Light:

So I went to speak to a local about these wind songs. Apparently, Inuit folklore claims that the Northern Lights produce sounds that shamans were once able to manipulate in order to create their own songs. The sounds of the Lights represent the spirits of the dead, either playing games or trying to communicate with the living. Although this story greatly inspired me, I discovered the source of these sounds the next day. There were intricate geometric formations of hollow metal bars outside the school used for the stairs and ramp. For some reason, holes were drilled into specific locations along the poles. Hence, they acted like wind instruments. As the wind passed through the poles, they would emit different tones depending on their lengths. So the tones from different poles would interact to form harmonies. I wonder if the architect who designed this building knew in advance that s/he was creating a musical instrument or hidden sound installation.

Here is an excerpt from these beautiful wind songs
(This excerpt is taken from my multi-channel sound installation Soundscapes of Inukjuak that is currently on display in Montreal at L'Envers Gallery - 185 Van Horne)

But back to the Aurora Borealis.....

Sound recordist Stephen McGreevy has proven that the lights do actually produce sounds. He refers to them as "naturally-occurring radio signals" or "whistlers". Many witnesses compare these sounds to radio static, a small animal rustling through dry grass and leaves, or the crinkling of cellophane wrapper.

McGreevy writes:
"Natural Radio," a term coined in the late 1980's by California amateur listener and researcher Michael Mideke, describes naturally-occurring electromagnetic (radio) signals emanating from lightning storms, aurora (The Northern and Southern Lights), and Earth's magnetic-field (the magnetosphere). Conditions within Earth's magnetosphere and between the Sun and the Earth are called "space-weather."

The majority of Earth's natural radio emissions audible with ground-based radio receivers occur in the extremely-low-frequency and very-low-frequency (ELF/VLF) radio spectrum - specifically, at AUDIO frequencies between approximately 100 to 10,000 cycles-per second (0.1--10 kHz). Unlike sound waves which are vibrations of air molecules that our ears are sensitive to, natural radio waves are vibrations of electric and magnetic energy (radio waves) which - though occurring at the same frequencies as sound - cannot be listened to without a fairly simple radio receiver to convert the natural radio signals directly into sound.

Whistlers are magnificent sounding bursts of ELF/VLF radio energy initiated by lightning strikes which "fall" in pitch. A whistler, as heard in the audio output from a VLF "whistler receiver," generally falls lower in pitch, from as high as the middle-to-upper frequency range of our hearing downward to a low pitch of a couple hundred cycles-per-second (Hz). Measured in frequency terms, a whistler can begin at over 10,000 Hz and fall to less than 200 Hz, though the majority are heard from 6,000 down to 500 Hz. Whistlers can tell scientists a great deal of the space environment between the Sun and the Earth and also about Earth's magnetosphere.

The causes of whistlers are generally well known today though not yet completely understood. What is clear is that whistlers owe their existence to lightning storms. Lightning stroke energy happens at all electromagnetic frequencies simultaneously--that is, from "DC to Light." Indeed, the Earth is literally bathed in lightning-stroke radio energy from an estimated 1,500 to 2,000 lightning storms in progress at any given time, triggering over a million lightning strikes daily. The total energy output of lightning storms far exceeds the combined power output of all man-made radio signals and electric power generated from power plants.

Whistlers also owe their existence to Earth's magnetic field (magnetosphere), which surrounds the planet like an enormous glove, and also to the Sun. Streaming from the Sun is the Solar Wind, which consists of energy and charged particles, called ions. And so, the combination of the Sun's Solar Wind, the Earth's magnnetosphere surrounding the entire Planet, and lightning storms all interact to create the intriguing sounds and great varieties of whistlers. (http://www.auroralchorus.com/vlfstory.htm)

This video gives a good explanation of McGreever's work along with sound clips:

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