The singing dunes
Lurking within the Badain Jaran desert of China amongst some of the tallest stationary dunes on the planet (up to 500 metres tall) are rare musical dunes, that boom and sing as you slide down them because of a poorly understood mechanism. The noise resulting is loud (up to 105 decibels) and deep, somewhat like a propeller plane and can last for up to a minute. One factor that certainly inhibits the property is water between the sand grains, after a rainfall for example. The structure of the dunes is crucial, as is the type of sand forming them. The noise can only be generated by creating an avalanche on the steep leeward side of the dune.
Loz
Image credit: Guo Qi
Paper on the desert and geomorphology of the dunes, free access: http://www.casnw.net/outside/keyan/desert/人员组成/董治宝.files/已发表论文/Geomorphology%20of%20the%20megadunes%20in%20the%20Badain%20Jaran%20Desert.pdf