Located 7 kilometres north of Dunhuang city, Mingsha Shan (Echoing-Sand Mountain) is part of the Gobi Desert region with an area spanning 200 square kilometres. The highest peak is 1715 metres above sea level. Mingsha Shan gets its name from the singing sound of people treading or slide on the surface of the sand. The sand mountains are formed by drifting dunes and the sands have five different colors of red, yellow, green, white and black.
There are various theories about the singing sand mechanism. It has been proposed that the sound frequency is controlled by the shear rate. Others have suggested that the frequency of vibration is related to the thickness of the dry surface layer of sand. The sound waves bounce back and forth between the surface of the dune and the surface of the moist layer, creating a resonance that increases the sound’s volume. The noise may be generated by friction between the grains or by the compression of air between them. (Wiki)