Leonid MAC '99 - News on the Leonid shower. For many years, stubborn rumours persisted that it was possible to hear bright fireballs at the same time when spotting the meteor. A hissing sound was often reported, sometimes so loudly that it drew attention to the fireball itself. These anecdotes were often dismissed on grounds that it takes sound a long time to travel the distance of a few hundred kilometers between fireball and observer, while the light arrives almost instantaneously. Some researchers, however, speculated that radio signals with audible frequencies might be emitted by the meteors, which then could interact with nearby transducers to cause an audible sound.
Radio signals are a form of electromagnetic waves and travel with the speed of light.
Now, in the upcoming issue of Earth, Moon and Planets, Colin Price and Moshe Blum at Tel Aviv University report the detection of numerous radio signals at the time of the 1999 Leonid meteor storm. Sure enough, these signals peak at 500 Hz and at 10,000 Hz. The audible range is 20-20,000 Hz. This is unlike radio signals from distant lightnings, which have a single peak between 5,000-10,000 Hz, many of which were detected at the same time. Interestingly enough, the rate of meteor detections was highest at the time of the meteor storm, and only few detections were reported in the night prior to the storm.