Q: Does the aurora make sounds?

This question is always good for a lively discussion among residents of the north. So far, attempts to record sound during aurora have failed to produce any proof that such sounds exist, but it is hard to ignore the numerous reports that go back centuries.

There are generally two types of sounds reported to accompany the aurora borealis. The first is a swishing sound that changes with movements in that auroral display. The second type is a crackling sound, like static electricity makes.

The problem with claims of sound that changes in time with auroral movements is that the aurora is a long ways away (100 km/60 miles), so if sound was coming from the aurora borealis, there would be a long delay between the auroral movement and the sound arriving at the listener's ears, just as thunder arrives long after a distant lightning flash is observed. There is also the small detail that the air between us and the aurora is far too thin to carry sound over such long distances. Therefore, if this kind of sound exists, it must be created very near to the observer.

The most likely explanation for this type of sound is that it is created inside the observer's head: not a figment of the imagination, but rather leakage of the electrical impulses from the nerves in the eye (carrying images of the aurora to the brain) into the part of the brain the processes sound. In a very quiet environment, there are no sound signals for the brain to process, so it notices these tiny leakage signals and the result is sounds that change in time with the aurora. This explanation was actually tested by some early explorers, who found that the sound went away if their eyes were covered.

The second type of sound is more mysterious. A crackling sound, like static electricity sparking, might be explained by the strong electric and magnetic fields associated with the aurora, but so far theories and measurements have not provided a satisfactory explanation. Research continues.