Snow sounds when rubbing or impacting a snow bed

Abstract

The acoustic emissions from rubbing the ends of baseball bats, thin wood rods, and the soles of rubber boots on a snow bed were recorded and analyzed. The same analysis was also extended to the acoustic emissions from impacting a snow bed by small pestles and by subjecting a snow bed to relatively large stresses by stepping on it with shoes of variable rigidity. It is shown that when a snow bed is lightly rubbed, the acoustic emissions originate from vibration mode excitation in the rubbing body. It is argued that when highly granular cold snow is impacted by a small pestle, the acoustic emissions could originate with mode excitation in granule vibration bands around the pestle end, as in the case of impacted singing sands. Layers of highly granular and rounded snow pellets, seemingly formed from frozen raindrops, could contribute especially to snow avalanches. When walking on a snow bed, the acoustic emissions include squeaky sounds that originate from mode excitation in the shoe sole and crunchy and squeally sounds that could originate with crack growth and crystal dislocation processes in the sheared matrix of snow grains and grain bonds.