WEEK 6 : TASK 2 - BOOMING SAND

http://www.pbs.org/wgbh/nova/sciencenow/3204/04.html
Have you ever been in the desert ? If you have, you may have heard loud sounds and thought that was the wind. But in the fact, those sounds don’t come from the wind but from the sand. We can not realize them because they are too general. And the question was made here is how come those sounds come from the sand and why it happens. No one can explain.
An account of engineers from California came a desert to find out mysterious noises and describe what booming sand does. First of all, they examined the desert by walking around on top of sand dunes. Then they carried out methods to identify origin of those noises. Their prime theory is the booming sand is doing really like a musical instrument that the sands on the surface is like vibrate strings and the hard surface below is like the body of the musical instrument. When the sands on the surface moves, they hit each other and make noises as when strings ring. Continuously, they made another trial ; they slid down from the top of dunes. At the beginning, they heard nothing, but then noises started to be louder and clearer. They called it the dunes’ music. They used some devices to record measure these noises. They pitched a stick into the hard part below the surface of the sand to measure and identify their levels. And the frequency is often equal to musical notes G. They said these sounds changed day by day and over last years it happened from dunes to dunes. They tried to figure out how much space they are between the top where the sands lose and hard surface down below. After 2 years, frequently visit to 3 of the 30 booming sand, they investigated many dunes that were 150 feet high and collected many important information to solve this phenomenon but it seems to be hopeless. Evidences showed that those sounds usually changes and they are same musical notes such as E, F, G. Anyway, they are still trying to discover mysteries about the booming sand and confirm their theories.