Sferics are Earth’s natural static – bursts of radio waves emitted by lightning. The name is a shortening of ‘atmospheric’ disturbances. They take the form of very low frequency (VLF) radio waves, typically between 0.1-10 kHz, and travel thousands of miles between the ground and ionosphere. A VLF receiver allows you to hear sferics at any time; lightning strikes around the world approximately 44 times per second. Sferics sound like little crackles and pops.
In September 2021, I built a series of VLF (very low frequency) radio receivers using recipes by Dan Tapper and Mark M0WGF. These antennas took the form of loops of magnet wire housed in a bicycle tire, copper wire and a hula hoop wrapped in electrical tape, 10 meters of ribbon cable crimped in a circle. Using these antennas, plugged into an audio recorder, I made a series of recordings in several locations in Cumbria whilst on a residency with Full of Noises. The recordings are set alongside spectrograms and interpretations. Sferics appear as vertical lines; the bright horizontal line near the top of the image is inaudible but likely a 19kHz pilot signal for stereo broadcasting FM radio.
To mark Earth Day 2022, I used these recordings in a new audio artwork 'Searching for Sferics', which documents the project through voice, radio and field recordings.
Cooke's Studio, Barrow-in-Furness
Ribbon antenna hung from the balcony of a building. With the antenna facing west from this and other locations, you could hear Radio 4 broadcasts clearly, alongside data modes and interference.
Barrow Park, Barrow-in-Furness
Hoop antenna hung in a tree on the highest point of Barrow Park. With the hoop facing west, we hear several radio stations and the hum of mains electricity in the town alongside data modes, telephone signals and sferics.
Piel Island, Barrow-in-Furness
Hoop antenna on the lowest wall of Piel Castle, half a mile from the mainland. Rustling sounds due to wind? Clear sferics, low hum of electricity from local cottages. No commercial radio or data packets audible.
South Walney Nature Reserve, Barrow-in-Furness
Hoop attached to wooden seal observation decking in nature reserve, 7 miles from Barrow center, 4 miles from closest houses, 1 mile from caravan park. Clear recording of sferics with minimal mains hum.
Hoad Hill, Ulverston
Hoop antenna held in hand on Ulverston's Hoad Hill, under the John Barrow monument. Mains hum, clear repetitive data signals, possible wind roar. Crispy sferics.
Resources & References
‘VLF: A Sound Artist's Guide’, Dan Tapper, 2015
Recipe to build a simple VLF receiver from home
'Earth Sound Earth Signal', Douglas Kahn, 2013
Book discussing artists, engineers and scientists interested in natural radio
‘Listening beyond radio, listening beyond history’, Kate Donovan, 2020
An audio essay imagining alternative histories of listening to natural radio
‘Sferics And Thunder Alberta’, Stephen P. McGreevy, 1996
Spectacular natural radio recordings