Crunch of Snow as a Natural Phenomenon: Acoustics of Ice Crystals The characteristic sound accompanying steps on snow cover in cold weather is not just background acoustics, but a complex physical phenomenon associated with the mechanical destruction of the ice matrix and the generation of sound waves in a wide frequency range. The crunch of snow is a kind of acoustic thermometer and an indicator of its structural properties. 1. Physical-mechanical foundations of sound formation The crunch occurs at the moment of deformation and destruction of the snow cover under load (footstep, ski, tire). This is a multistage process: Plastic deformation and brittle failure. The snow cover is a porous medium consisting of ice crystals (snowflakes) and grains connected by snow bridges (fusing bonds). At a temperature close to 0°C, these bonds are relatively plastic, and crystals can deform and slide against each other almost silently. However, with decreasing temperature, ice becomes brittle, and the bonds between crystals become rigid. The mechanism of "microexplosions". Under the pressure of the foot, the sharp tips of the crystals concentrate stress at points of contact. Immediate brittle failure (scaling) of these tips and snow bridges occurs. The released elastic energy causes microvibrations of the separated fragments and the entire ice lattice. These microvibrations are the primary source of sound. Acoustic studies have shown that one step causes the destruction of hundreds of thousands of such microcontacts. The role of temperature. Temperature is a key factor determining the character of the sound. This is due to the fundamental property of ice: with decreasing temperature, its brittleness and Young's modulus (a measure of stiffness) increase. More rigid and brittle ice generates sound waves of greater amplitude and higher frequency upon destruction. 2. Dependence of sound on temperature: acoustic scale Observations and experiments (including those conducted in the Soviet ... Read more