Geophysical Electrophonics

Definition:

The production of audible noises of various kinds through direct conversion by transduction of very low frequency electromagnetic energy generated by a number of geophysical phenomena.


Brief Introduction

The first recognition that the production of certain unusual sounds was a scientific mystery came when Edmund Halley (of comet fame) realised that strange noises coincident with a large meteor fireball seen throughout much of England in 1719 could not be transmitted instantaneously over distances in excess of 100 km. He dismissed the effect as psychological and for two and a half centuries his mistaken opinion was upheld by many meteor scientists.

A viable physical explanation was not found until 1979 when Colin Keay in Australia investigated reports that a huge fireball which passed over Sydney and Newcastle, NSW, a year earlier had been heard while it was in view by many observers. He successfully argued that large meteor fireballs must generate very low frequency (ELF/VLF) electromagnetic energy which which witnesses may hear if a suitable transducer happens to be on or close to them. This purely physical process most likely explains acoustic anomalies connected with various other geophysical phenomena.

Keay's novel mechanism for the generation of the required energy in the turbulent trails of large meteor fireballs was upheld by theorist Vitaly Bronshten in Russia. Laboratory work on the transduction process and observations of the actual radiation verified the overall concept, which has now become widely accepted.

What phenomena may produce electrophonic noises?

Large meteors (bolides) Look at: History, Explanation
Very bright auroras Look at: Background, Display
Nearby lightning Not ready yet
Earthquakes (animal alarm) Not ready yet
Close comets Not ready yet

Copyright 1997 Colin Keay.
All rights reserved except where otherwise acknowledged.