Snow falling in Scotland (21 seconds)
Under water, snowfall has a unique sound when compared to other forms of precipitation. Despite the different sizes and shapes on individual snowflakes, the sound made when individual flakes fall upon the surface of a freshwater lake are quite similar. On the ground, newly fallen snow acts as a sound-absorbing material, which minimizes sound over its surface. This is due to the trapped air between the individual crystalline flakes which act to trap sound waves and dampen vibrations. Once it is blown around by the wind and exposed to sunshine, snow hardens and its sound-softening quality diminishes. Snow cover as thin as 2 centimeters (0.79 in) thick changes the acoustic properties of a landscape. Studies concerning the acoustic properties of snow have revealed that loud sounds, such as from a pistol, can be used to measure snow cover permeability and depth. Within motion pictures, the sound of walking through snow is simulated using cornstarch, salt, or cat litter. When the temperature falls below −10 °C (14.0 °F), snow will squeak when walked upon due to the crushing of the ice crystals within the snow. If covered by a layer of freezing rain, the hardened frozen surface acts to echo sounds, similar to concrete.
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