Measurements of Acoustic Properties of Hard-Pack Snow

Abstract

AbstractThree experiments were conducted to assess acoustic properties of hard-pack snow. One test involved transmission of acoustic signals in the frequency range 100-20 000 Hz through natural snow-pack in order to measure signal loss of a point acoustic source. At all frequencies the relatively high-energy input signal decays rapidly by energy dissipation, with nominal diffusion occurring at large distances from the source. Signal persistence is greatest in the frequency range 100-200 Hz, In a second test, acoustic bursts in snow columns under deformation were recorded. Spectrum analysis in the frequency range 500-14000 Hz reveals dominance of signal amplitudes at frequencies between 1 000 and 10 000 Hz. This dominance is attributed to the strong attenuation properties of snow and suggests the use of waveguide or collector techniques to monitor natural acoustic emissions in snow-pack. In a third test several waveguide geometries and materials were evaluated for their acoustic signal interception and transmission characteristics. In general, metallic waveguides show the least attenuation of the configurations tested.