Abstract
Sound-producing sand grains called singing sands or squeaking sands constitute puzzling physical phenomena. They produce manifest acoustic emissions of 500 to 1000 Hz when sheared. Eolian quartz sand material were used for the examination of friction characteristics as well as surface textures with progressive abrasion by washing and polishing. Sufficiently polished quartz sands produced squeaking sound and demonstrated increases of porosity, angle of repose and angle of internal friction. However, they show lower friction when submerged in water. It is probably because that the inter-solid friction due to adhesion or pressure solution was lowered by the water film between the grains. In addition, well-polished quartz sands demonstrated a distinct cyclic stick-slip motion under slow shear using less stiff loading system. The higher inter-solid friction and the cyclic stick-slip motion are strongly suggested as the cause of singing sands rather than roundness or sorting of sands.
