What Causes Shooting Star Sounds?

Although the news story yesterday was on meteors another story of equal interest has arisen on a similar topic. Rather than trying to work out where the meteorites originated this paper is more concerned about what they do when they get here. When a meteoroid of sufficient size falls through the atmosphere it can create quite an extreme amount of light. When people see this light they sometimes describe hearing a popping or sizzling sound simultaneously. This cannot be noise created directly by the meteoroid as this would take a couple of minutes to reach the observer and certainly wouldn’t occur at the same time as the light flash. The most reasonable explanation is that the electromagnetic waves the meteor generates must be interacting to make a sound waves in the local area around the observer.

It has always been believed the energy put out be meteors was almost entirely in the radio frequency range although there are few experiments that conclusively prove this fact. The idea that has been suggested is that of photoacoustic coupling where the radiation given off by the fireball can cause some materials to produce noises. By performing light intensity observations on incoming meteors it was seen that the brightness oscillates over 50 times a second. It has been numerically shown that the light given off, when modulated to these kinds of frequencies, has the possibility of transferring enough radiative heat to cause dielectric materials, such as hair or clothes (really any fibre) to produce noise that should be audible for humans. By measuring the photoacoustic ability of common materials, and proving they matched with the theoretical predications, it was concluded that an observer, in a quiet location, with a suitable amount of dielectric substances around them could very well hear a sound that occurred concurrently with the light from a meteor.

Paper links: Photoacoustic Sounds from Meteors

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