Blast noise propagation above a snow cover at Haslemoen, Norway

Abstract

During the short-range winter measurements at Haslemoen, Norway, a series of blast wave forms produced by 1-kg charges of C4 explosive fired 2 m above a dry snow cover 11 to 20 cm thick were recorded after propagating horizontally 100 to 1400 m. In attempting to model these experiments, it was found that the usual viscoelastic treatment of the ground was unable to match the recorded wave forms. A rigid-porous model of the snow cover was required to obtain good agreement. The measured wave forms, with a peak frequency around 50 Hz, show pulse broadening effects similar to those previously seen in pistol shot experiments using higher frequency waves over shorter propagation distances. The modeling predicts an average snow cover depth of 15 cm and effective flow resistivities of 30−41 kPa<th>s<th>m−2, in agreement with snow pit observations and with previous acoustic measurements over snow. For propagation in the upwind direction, the pulse broadening caused by the snow cover interaction is lessened, but the overall amplitude decay is greater because of refraction of the blast waves.