'Natural Radio' is the name given to naturally occuring radio emissions which can be found in the ELF and VLF frequency bands. The ELF (Extra Low Frequency) band extends from zero frequency (i.e. DC) up to 3kHz, and the VLF band extends from 3kHz up to 30kHz. In actual fact, as far as natural radio is concerned, these two bands overlap.
You will notice that the frequencies concerned here are roughly the same as the range of frequencies you can hear- but it important to grasp that natural radio phenomena are propagated as a radio wave and sounds are propagated as pressure waves in the air.
Natural Radio was discovered almost as soon as landline communication came into widespread use, in the latter part of the last century. Operators, forced to listen continuously to their long overhead telegraph lines, heard sounds that, at the time, were assumed to be originating in the equipment. The names that they gave to these sounds, tweeks and whistlers, are still used today. The effect has been seriously studied at various times, notably by Storey in the 1950's, and nowadays by many University project teams. There is an increasing number of amateurs who listen to the sounds purely to marvel at the eery beauty of them.
Some of the sounds consist of falling or rising tones, others are more complex- the sounds can resemble a flock of birds, the barking of dogs, or the sighing of waves on the sea shore. The echoes and reverberations of these sounds often lend them a particularly sureal character.
This site is devoted to a description of the different manifestations of Natural Radio phenomena, what makes them occur, how we can detect them, and how to predict when they will happen. You can also listen to recordings which I have made of some of the different sounds.
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Last Modified 07/01/2008
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