Experimental study of surface texture and resonance mechanism of booming sand

摘要

The sound-producing mechanism of booming sand has long been a pending problem in the blown sand physics. Based on the earlier researches, the authors collected some silent sand samples from Tengger Desert, Australian Desert, Kuwait Desert, beaches of Hainan Island and Japanese coast as well as the soundless booming sand samples from the Mingsha Mountain in Dunhuang to make washing experiments. In the meantime the chemical corrosion experiment of glass micro-spheres, surface coating experiment and SEM examination were also conducted. The experimental results show that the sound production of booming sand seems to have nothing to do with the presence of SiO_2 gel on the surface of sand grains and unrelated to the surface chemical composition of sand grains but is related to the resonance cavities formed by porous (pit-like) physical structure resulting from a number of factors such as wind erosion, water erosion, chemical corrosion and SiO_2 gel deposition, etc. Its resonance mechanism is similar to that of Hemholz resonance cavity. Under the action of external forces, numerous spherical and sand grains with smooth surface and porous surface are set in motion and rub with each other to produce extremely weak vibration sound and then become audible sound by human ears through the magnification of surface cavity resonance. However the booming sands may lose their resonance mechanism and become silent sand due to the damping action caused by the invasion of finer particles such as dust and clay into surface holes of sand grains. Therefore, clearing away fine pollutants on the quartz grain surface is an effective way to make silent sand emit audible sound.