Like the sound of horns and tribal drums calling for war, sometimes the endless dunes of the Sahara emit a strange penetrating symphony that fills the air with low frequency vibrations.
The once mysterious phenomenon, documented centuries ago from Marco Polo to Charles Darwin, is produced by the upper layers of drier sand moving over the deepest ones. When a certain level of dryness is reached, the desert itself cries out, like an avalanche rumbling that echoes across miles of emptiness:
The video belongs to the fascinating series Africa from BBC, directed and narrated by the legendary David Attenborough. So far, this is probably the best footage of this eerie sound effect.
The intriguing sonic booms have been reported in other parts of the world, from Mongolia to the Atacama Desert in Chile. In addition, a recent scientific research could recreate their characteristic noise artificially in a laboratory, and confirmed that the pitch of the sound depends on the thickness of the sand grains. This way, each desert has its own musical record.