have you heard of booming sand?
some types of sand make a vibration, or even a musical whistling, booming, croaking or squeaking.
some interesting facts about singing sand (from nova online):
· only around 30 "booming" dunes are known worldwide—in deserts and on beaches in hawaii, north and south america, africa, the middle east, and asia
· booming sand dunes sound like instruments because, as opposed to squeaking sands, the noise they produce lasts longer (up to 15 minutes in large dunes) and it emanates at a single, steady musical tone
· booming sand starts with a dune made of sand that has traveled long distances from its original source
· the sand's lengthy, windy journey means that grains deposited on the surface of the dune are extremely round, smooth, and uniform
· a desert rainstorm must take place, washing dust and other foreign particles from among the surface grains; the topmost sand must then dry out over a period of weeks while the sand beneath remains relatively moist
· booming can be heard more than six miles away
· in squeaking sand, noise-producing displacement can occur merely by stepping on the sand with your foot