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Snow is a porous sound absorbing material with ice as its one of the most important constituting material. The progressive deformation in the snowpack induce initial damage subsequently leads to fracture propagation and avalanche release. During the process of induced damage, stress waves are generated and can propagate through ice network as well as through air. Biots theory of acoustic wave propagation in porous media suggets that there exist three types of waves namely: longitudinal and shear/transverse wave through solid network and longitudinal wave through pore netwok. Snow microstructure affects the propagation behaviour of all the three type of waves. Further, depending upon the mode of propagation, attenuation of the acoustic waves varies and hence affects their detection. Therefore determination of the acoustic properties of snow are extremely useful to understand the snow-acoustic interaction and propagation behaviour of acoustic waves. In the present study acoustic properties of snow representing propagation through air are simulated and validated through impedance tube experiments. Snow sample is prepared with extreme care using sieved snow. The snow used is transported to cold laboratory via helicopter from greater Himalaya in insulated boxes. After taking the measurement, 3D snow micro-structure of the same sample was captured using X-ray micro- computer tomography (micro-CT). Scanning and reconstruction resolutions for 3D microstructure is kept at 35.03 m. The simulations are carried out using using Johnson Champoux and Allard (JCA) model. This model is based on five geometrical parameters of snow structure and these parameters were derived from the actual snow microstructure. A commercially available finite element analysis (FEA) software COMSOL was used for simulating acoustic properties. The variation in the acoustic properties such as absorption and reflection coefficient are analysed as a function of frequency. It was observed that simulated behaviour of snow is quite close to the experimental results. The effect of porous domain thickness and porosity on the acoustic absorption coefficient was also investigated for a frequency range 64-6300 Hz. It is observed that resonance peaks disappeared for porous domain having thickness greater than 20 cm due to attenuation of wave and unable to take part in formation of standing wave. At the same time absorption coefficient at snow-air interface is found to be increasing with porosity respectively.
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