Skywatchers hearing things
As recently as the 1970s, people who reported hearing a sound as a meteor passed were routinely dismissed as crackpots, according to the report by Keay, published in the journal Asteroids, Comets, Meteors.
But after a large meteor passed over New South Wales in 1978, hundreds of anecdotal reports from people who claim they heard the meteor flooded the news media. Keay analyzed 36 of these reports and drew some important conclusions.
Meteors obviously release electromagnetic radiation in the visible portion of the spectrum, but the fact that they also release very low frequency (VLF) radio waves, below 30 kilohertz, is less known and less studied.
Because these VLF radio waves travel at the speed of light (not at the speed of sound), they arrive at the same time observers see a meteor passing overhead. But in order to be heard by hundreds of people, Keay deduced, radio waves need a "transducer," or some physical object that could create a sound.
Under laboratory conditions, Keay was able to do just that: He created rustling sounds in ordinary objects by exposing them to VLF radiation. Aluminum foil, plant foliage such as pine needles, thin wires — even dry, frizzy hair — produced sounds that were easily heard. This phenomenon is known as electrophonics.
Wire-framed eyeglasses seem to be particularly sensitive to VLF radiation: "When I was out [viewing the Leonid meteor showers in 1999], I had my head back on the ground and heard a sizzling sound," one observer reported. "My head was close to grass and leaves and I wear wire-frame glasses as well. The sound was definitely simultaneous with the observation of a rather large streak."...
