scientist plan CD of ‘singing’ sand dunes

Scientist plan CD of ‘singing’ sand dunes
It might knock Coldplay or Kanye West off the top of the charts, but physicist who they say have cracked the riddle of “singing” sand dunes are compiling a CD of sand music. The team says their new theory allows them to predict the notes that different dunes will make. Sand dunes in certain parts of the world are notorious for the noises they make as sand avalanches down their sides. Some emit low powerful booms, others sound like drum rolls or galloping horses, and some are even tuneful. These dunes songs have been reported to last for up to 15 minutes. Physicist knows that it is the avalanches that set the grains humming, but the precise mechanism has remained controversial. Stephane Douady of the French national research agency shipped sand from Moroccan singing dunes back to its lab to investigate. They found that they could play notes by pushing the sand by hand. That put to rest to one theory that the noise was the result of the entire dune resonating. But after the month of singing, the sand seemed to lose their voice. The singing grains were round with a smooth coating of silicon, iron and manganese, which probably formed on the sand when the dunes once lay beneath an ancient ocean. But in the muted grains this coat had been worn away, which explains why only some dunes can sing, says Douady.