For centuries, folk tales and travellers have mentioned the sounds associated with aurora borealis, the northern lights. Finnish researchers have now recorded and pinned down the location of the source of the noises.
The researchers showed that the sounds are audible to the human ear and are produced around 70 metres above the ground.
The Aalto University researchers placed microphones at three different locations above ground, recording sounds and calculating their location.
They proved that people are able to hear sounds associated with the northern lights, despite the distance between earth and the aurora borealis. It has previously been supposed that the sounds are so high-pitched that they cannot be heard by humans.
“Our research proves that the source of the sounds that are associated with the aurora borealis we see is likely caused by the same energetic particles from the sun that create the northern lights far away in the sky. These particles or the geomagnetic disturbance produced by them seem to create sound much closer to the ground”, said Professor Unto K. Laine from Aalto University.
The precise cause of the sounds remain unclear. Because they are inconsistently reproduced, researchers believe that different mechanisms could be at play. The sounds tend to be so faint that listeners have to concentrate hard to distinguish them from ambient noise.
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